* [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users
@ 2025-09-05 9:02 Marco Crivellari
2025-09-05 9:02 ` [PATCH 1/3] fs: replace use of system_unbound_wq with system_dfl_wq Marco Crivellari
` (3 more replies)
0 siblings, 4 replies; 6+ messages in thread
From: Marco Crivellari @ 2025-09-05 9:02 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: Tejun Heo, Lai Jiangshan, Frederic Weisbecker,
Sebastian Andrzej Siewior, Marco Crivellari, Michal Hocko,
Alexander Viro, Christian Brauner
Hi!
Below is a summary of a discussion about the Workqueue API and cpu isolation
considerations. Details and more information are available here:
"workqueue: Always use wq_select_unbound_cpu() for WORK_CPU_UNBOUND."
https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/
=== Current situation: problems ===
Let's consider a nohz_full system with isolated CPUs: wq_unbound_cpumask is
set to the housekeeping CPUs, for !WQ_UNBOUND the local CPU is selected.
This leads to different scenarios if a work item is scheduled on an isolated
CPU where "delay" value is 0 or greater then 0:
schedule_delayed_work(, 0);
This will be handled by __queue_work() that will queue the work item on the
current local (isolated) CPU, while:
schedule_delayed_work(, 1);
Will move the timer on an housekeeping CPU, and schedule the work there.
Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistentcy cannot be addressed without refactoring the API.
=== Plan and future plans ===
This patchset is the first stone on a refactoring needed in order to
address the points aforementioned; it will have a positive impact also
on the cpu isolation, in the long term, moving away percpu workqueue in
favor to an unbound model.
These are the main steps:
1) API refactoring (that this patch is introducing)
- Make more clear and uniform the system wq names, both per-cpu and
unbound. This to avoid any possible confusion on what should be
used.
- Introduction of WQ_PERCPU: this flag is the complement of WQ_UNBOUND,
introduced in this patchset and used on all the callers that are not
currently using WQ_UNBOUND.
WQ_UNBOUND will be removed in a future release cycle.
Most users don't need to be per-cpu, because they don't have
locality requirements, because of that, a next future step will be
make "unbound" the default behavior.
2) Check who really needs to be per-cpu
- Remove the WQ_PERCPU flag when is not strictly required.
3) Add a new API (prefer local cpu)
- There are users that don't require a local execution, like mentioned
above; despite that, local execution yeld to performance gain.
This new API will prefer the local execution, without requiring it.
=== Introduced Changes by this series ===
1) [P 1-2] Replace use of system_wq and system_unbound_wq
system_wq is a per-CPU workqueue, but his name is not clear.
system_unbound_wq is to be used when locality is not required.
Because of that, system_wq has been renamed in system_percpu_wq, and
system_unbound_wq has been renamed in system_dfl_wq.
2) [P 3] add WQ_PERCPU to remaining alloc_workqueue() users
Every alloc_workqueue() caller should use one among WQ_PERCPU or
WQ_UNBOUND. This is actually enforced warning if both or none of them
are present at the same time.
WQ_UNBOUND will be removed in a next release cycle.
=== For Maintainers ===
There are prerequisites for this series, already merged in the master branch.
The commits are:
128ea9f6ccfb6960293ae4212f4f97165e42222d ("workqueue: Add system_percpu_wq and
system_dfl_wq")
930c2ea566aff59e962c50b2421d5fcc3b98b8be ("workqueue: Add new WQ_PERCPU flag")
Thanks!
Marco Crivellari (3):
fs: replace use of system_unbound_wq with system_dfl_wq
fs: replace use of system_wq with system_percpu_wq
fs: WQ_PERCPU added to alloc_workqueue users
fs/afs/callback.c | 4 ++--
fs/afs/main.c | 4 ++--
fs/afs/write.c | 2 +-
fs/aio.c | 2 +-
fs/bcachefs/btree_write_buffer.c | 2 +-
fs/bcachefs/io_read.c | 12 ++++++------
fs/bcachefs/journal_io.c | 2 +-
fs/bcachefs/super.c | 10 +++++-----
fs/btrfs/async-thread.c | 3 +--
fs/btrfs/block-group.c | 2 +-
fs/btrfs/disk-io.c | 2 +-
fs/btrfs/extent_map.c | 2 +-
fs/btrfs/space-info.c | 4 ++--
fs/btrfs/zoned.c | 2 +-
fs/ceph/super.c | 2 +-
fs/dlm/lowcomms.c | 2 +-
fs/dlm/main.c | 2 +-
fs/ext4/mballoc.c | 2 +-
fs/fs-writeback.c | 4 ++--
fs/fuse/dev.c | 2 +-
fs/fuse/inode.c | 2 +-
fs/gfs2/main.c | 5 +++--
fs/gfs2/ops_fstype.c | 6 ++++--
fs/netfs/objects.c | 2 +-
fs/netfs/read_collect.c | 2 +-
fs/netfs/write_collect.c | 2 +-
fs/nfs/namespace.c | 2 +-
fs/nfs/nfs4renewd.c | 2 +-
fs/nfsd/filecache.c | 2 +-
fs/notify/mark.c | 4 ++--
fs/ocfs2/dlm/dlmdomain.c | 3 ++-
fs/ocfs2/dlmfs/dlmfs.c | 3 ++-
fs/quota/dquot.c | 2 +-
fs/smb/client/cifsfs.c | 16 +++++++++++-----
fs/smb/server/ksmbd_work.c | 2 +-
fs/smb/server/transport_rdma.c | 3 ++-
fs/super.c | 3 ++-
fs/verity/verify.c | 2 +-
fs/xfs/xfs_log.c | 3 +--
fs/xfs/xfs_mru_cache.c | 3 ++-
fs/xfs/xfs_super.c | 15 ++++++++-------
41 files changed, 82 insertions(+), 69 deletions(-)
--
2.51.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 1/3] fs: replace use of system_unbound_wq with system_dfl_wq
2025-09-05 9:02 [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users Marco Crivellari
@ 2025-09-05 9:02 ` Marco Crivellari
2025-09-05 9:02 ` [PATCH 2/3] fs: replace use of system_wq with system_percpu_wq Marco Crivellari
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Marco Crivellari @ 2025-09-05 9:02 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: Tejun Heo, Lai Jiangshan, Frederic Weisbecker,
Sebastian Andrzej Siewior, Marco Crivellari, Michal Hocko,
Alexander Viro, Christian Brauner
Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistentcy cannot be addressed without refactoring the API.
system_unbound_wq should be the default workqueue so as not to enforce
locality constraints for random work whenever it's not required.
Adding system_dfl_wq to encourage its use when unbound work should be used.
queue_work() / queue_delayed_work() / mod_delayed_work() will now use the
new unbound wq: whether the user still use the old wq a warn will be
printed along with a wq redirect to the new one.
The old system_unbound_wq will be kept for a few release cycles.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
fs/afs/callback.c | 4 ++--
fs/afs/write.c | 2 +-
fs/bcachefs/btree_write_buffer.c | 2 +-
fs/bcachefs/io_read.c | 12 ++++++------
fs/bcachefs/journal_io.c | 2 +-
fs/btrfs/block-group.c | 2 +-
fs/btrfs/extent_map.c | 2 +-
fs/btrfs/space-info.c | 4 ++--
fs/btrfs/zoned.c | 2 +-
fs/ext4/mballoc.c | 2 +-
fs/netfs/objects.c | 2 +-
fs/netfs/read_collect.c | 2 +-
fs/netfs/write_collect.c | 2 +-
fs/nfsd/filecache.c | 2 +-
fs/notify/mark.c | 4 ++--
fs/quota/dquot.c | 2 +-
16 files changed, 24 insertions(+), 24 deletions(-)
diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 69e1dd55b160..894d2bad6b6c 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -42,7 +42,7 @@ static void afs_volume_init_callback(struct afs_volume *volume)
list_for_each_entry(vnode, &volume->open_mmaps, cb_mmap_link) {
if (vnode->cb_v_check != atomic_read(&volume->cb_v_break)) {
afs_clear_cb_promise(vnode, afs_cb_promise_clear_vol_init_cb);
- queue_work(system_unbound_wq, &vnode->cb_work);
+ queue_work(system_dfl_wq, &vnode->cb_work);
}
}
@@ -90,7 +90,7 @@ void __afs_break_callback(struct afs_vnode *vnode, enum afs_cb_break_reason reas
if (reason != afs_cb_break_for_deleted &&
vnode->status.type == AFS_FTYPE_FILE &&
atomic_read(&vnode->cb_nr_mmap))
- queue_work(system_unbound_wq, &vnode->cb_work);
+ queue_work(system_dfl_wq, &vnode->cb_work);
trace_afs_cb_break(&vnode->fid, vnode->cb_break, reason, true);
} else {
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 18b0a9f1615e..fe3421435e05 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -172,7 +172,7 @@ static void afs_issue_write_worker(struct work_struct *work)
void afs_issue_write(struct netfs_io_subrequest *subreq)
{
subreq->work.func = afs_issue_write_worker;
- if (!queue_work(system_unbound_wq, &subreq->work))
+ if (!queue_work(system_dfl_wq, &subreq->work))
WARN_ON_ONCE(1);
}
diff --git a/fs/bcachefs/btree_write_buffer.c b/fs/bcachefs/btree_write_buffer.c
index adbe576ec77e..8b9cd4cfd488 100644
--- a/fs/bcachefs/btree_write_buffer.c
+++ b/fs/bcachefs/btree_write_buffer.c
@@ -822,7 +822,7 @@ int bch2_journal_keys_to_write_buffer_end(struct bch_fs *c, struct journal_keys_
if (bch2_btree_write_buffer_should_flush(c) &&
__bch2_write_ref_tryget(c, BCH_WRITE_REF_btree_write_buffer) &&
- !queue_work(system_unbound_wq, &c->btree_write_buffer.flush_work))
+ !queue_work(system_dfl_wq, &c->btree_write_buffer.flush_work))
bch2_write_ref_put(c, BCH_WRITE_REF_btree_write_buffer);
if (dst->wb == &wb->flushing)
diff --git a/fs/bcachefs/io_read.c b/fs/bcachefs/io_read.c
index 417bb0c7bbfa..1b05ad45220c 100644
--- a/fs/bcachefs/io_read.c
+++ b/fs/bcachefs/io_read.c
@@ -553,7 +553,7 @@ static void bch2_rbio_error(struct bch_read_bio *rbio,
if (bch2_err_matches(ret, BCH_ERR_data_read_retry)) {
bch2_rbio_punt(rbio, bch2_rbio_retry,
- RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+ RBIO_CONTEXT_UNBOUND, system_dfl_wq);
} else {
rbio = bch2_rbio_free(rbio);
@@ -833,13 +833,13 @@ static void __bch2_read_endio(struct work_struct *work)
memalloc_nofs_restore(nofs_flags);
return;
csum_err:
- bch2_rbio_punt(rbio, bch2_read_csum_err, RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+ bch2_rbio_punt(rbio, bch2_read_csum_err, RBIO_CONTEXT_UNBOUND, system_dfl_wq);
goto out;
decompression_err:
- bch2_rbio_punt(rbio, bch2_read_decompress_err, RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+ bch2_rbio_punt(rbio, bch2_read_decompress_err, RBIO_CONTEXT_UNBOUND, system_dfl_wq);
goto out;
decrypt_err:
- bch2_rbio_punt(rbio, bch2_read_decrypt_err, RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+ bch2_rbio_punt(rbio, bch2_read_decrypt_err, RBIO_CONTEXT_UNBOUND, system_dfl_wq);
goto out;
}
@@ -859,7 +859,7 @@ static void bch2_read_endio(struct bio *bio)
rbio->bio.bi_end_io = rbio->end_io;
if (unlikely(bio->bi_status)) {
- bch2_rbio_punt(rbio, bch2_read_io_err, RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+ bch2_rbio_punt(rbio, bch2_read_io_err, RBIO_CONTEXT_UNBOUND, system_dfl_wq);
return;
}
@@ -878,7 +878,7 @@ static void bch2_read_endio(struct bio *bio)
rbio->promote ||
crc_is_compressed(rbio->pick.crc) ||
bch2_csum_type_is_encryption(rbio->pick.crc.csum_type))
- context = RBIO_CONTEXT_UNBOUND, wq = system_unbound_wq;
+ context = RBIO_CONTEXT_UNBOUND, wq = system_dfl_wq;
else if (rbio->pick.crc.csum_type)
context = RBIO_CONTEXT_HIGHPRI, wq = system_highpri_wq;
diff --git a/fs/bcachefs/journal_io.c b/fs/bcachefs/journal_io.c
index 1b7961f4f609..298be7748e99 100644
--- a/fs/bcachefs/journal_io.c
+++ b/fs/bcachefs/journal_io.c
@@ -1256,7 +1256,7 @@ int bch2_journal_read(struct bch_fs *c,
percpu_ref_tryget(&ca->io_ref[READ]))
closure_call(&ca->journal.read,
bch2_journal_read_device,
- system_unbound_wq,
+ system_dfl_wq,
&jlist.cl);
else
degraded = true;
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index a8129f1ce78c..eb25a4acd54d 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -2026,7 +2026,7 @@ void btrfs_reclaim_bgs(struct btrfs_fs_info *fs_info)
btrfs_reclaim_sweep(fs_info);
spin_lock(&fs_info->unused_bgs_lock);
if (!list_empty(&fs_info->reclaim_bgs))
- queue_work(system_unbound_wq, &fs_info->reclaim_bgs_work);
+ queue_work(system_dfl_wq, &fs_info->reclaim_bgs_work);
spin_unlock(&fs_info->unused_bgs_lock);
}
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 7f46abbd6311..812823b93b66 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1373,7 +1373,7 @@ void btrfs_free_extent_maps(struct btrfs_fs_info *fs_info, long nr_to_scan)
if (atomic64_cmpxchg(&fs_info->em_shrinker_nr_to_scan, 0, nr_to_scan) != 0)
return;
- queue_work(system_unbound_wq, &fs_info->em_shrinker_work);
+ queue_work(system_dfl_wq, &fs_info->em_shrinker_work);
}
void btrfs_init_extent_map_shrinker_work(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index ff089e3e4103..719d8d13d63e 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -1764,7 +1764,7 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info,
space_info->flags,
orig_bytes, flush,
"enospc");
- queue_work(system_unbound_wq, async_work);
+ queue_work(system_dfl_wq, async_work);
}
} else {
list_add_tail(&ticket.list,
@@ -1781,7 +1781,7 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info,
need_preemptive_reclaim(fs_info, space_info)) {
trace_btrfs_trigger_flush(fs_info, space_info->flags,
orig_bytes, flush, "preempt");
- queue_work(system_unbound_wq,
+ queue_work(system_dfl_wq,
&fs_info->preempt_reclaim_work);
}
}
diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index fb8b8b29c169..7ab51a1e857e 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -2429,7 +2429,7 @@ void btrfs_schedule_zone_finish_bg(struct btrfs_block_group *bg,
atomic_inc(&eb->refs);
bg->last_eb = eb;
INIT_WORK(&bg->zone_finish_work, btrfs_zone_finish_endio_workfn);
- queue_work(system_unbound_wq, &bg->zone_finish_work);
+ queue_work(system_dfl_wq, &bg->zone_finish_work);
}
void btrfs_clear_data_reloc_bg(struct btrfs_block_group *bg)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 0d523e9fb3d5..689950520e28 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3927,7 +3927,7 @@ void ext4_process_freed_data(struct super_block *sb, tid_t commit_tid)
list_splice_tail(&freed_data_list, &sbi->s_discard_list);
spin_unlock(&sbi->s_md_lock);
if (wake)
- queue_work(system_unbound_wq, &sbi->s_discard_work);
+ queue_work(system_dfl_wq, &sbi->s_discard_work);
} else {
list_for_each_entry_safe(entry, tmp, &freed_data_list, efd_list)
kmem_cache_free(ext4_free_data_cachep, entry);
diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index dc6b41ef18b0..da9cf4747728 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -159,7 +159,7 @@ void netfs_put_request(struct netfs_io_request *rreq, bool was_async,
if (dead) {
if (was_async) {
rreq->work.func = netfs_free_request;
- if (!queue_work(system_unbound_wq, &rreq->work))
+ if (!queue_work(system_dfl_wq, &rreq->work))
WARN_ON(1);
} else {
netfs_free_request(&rreq->work);
diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c
index 23c75755ad4e..3f64a9f6c688 100644
--- a/fs/netfs/read_collect.c
+++ b/fs/netfs/read_collect.c
@@ -474,7 +474,7 @@ void netfs_wake_read_collector(struct netfs_io_request *rreq)
!test_bit(NETFS_RREQ_RETRYING, &rreq->flags)) {
if (!work_pending(&rreq->work)) {
netfs_get_request(rreq, netfs_rreq_trace_get_work);
- if (!queue_work(system_unbound_wq, &rreq->work))
+ if (!queue_work(system_dfl_wq, &rreq->work))
netfs_put_request(rreq, true, netfs_rreq_trace_put_work_nq);
}
} else {
diff --git a/fs/netfs/write_collect.c b/fs/netfs/write_collect.c
index 3fca59e6475d..7ef3859e36d0 100644
--- a/fs/netfs/write_collect.c
+++ b/fs/netfs/write_collect.c
@@ -451,7 +451,7 @@ void netfs_wake_write_collector(struct netfs_io_request *wreq, bool was_async)
{
if (!work_pending(&wreq->work)) {
netfs_get_request(wreq, netfs_rreq_trace_get_work);
- if (!queue_work(system_unbound_wq, &wreq->work))
+ if (!queue_work(system_dfl_wq, &wreq->work))
netfs_put_request(wreq, was_async, netfs_rreq_trace_put_work_nq);
}
}
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index ab85e6a2454f..910fde3240a9 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -113,7 +113,7 @@ static void
nfsd_file_schedule_laundrette(void)
{
if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags))
- queue_delayed_work(system_unbound_wq, &nfsd_filecache_laundrette,
+ queue_delayed_work(system_dfl_wq, &nfsd_filecache_laundrette,
NFSD_LAUNDRETTE_DELAY);
}
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 798340db69d7..55a03bb05aa1 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -428,7 +428,7 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
conn->destroy_next = connector_destroy_list;
connector_destroy_list = conn;
spin_unlock(&destroy_lock);
- queue_work(system_unbound_wq, &connector_reaper_work);
+ queue_work(system_dfl_wq, &connector_reaper_work);
}
/*
* Note that we didn't update flags telling whether inode cares about
@@ -439,7 +439,7 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
spin_lock(&destroy_lock);
list_add(&mark->g_list, &destroy_list);
spin_unlock(&destroy_lock);
- queue_delayed_work(system_unbound_wq, &reaper_work,
+ queue_delayed_work(system_dfl_wq, &reaper_work,
FSNOTIFY_REAPER_DELAY);
}
EXPORT_SYMBOL_GPL(fsnotify_put_mark);
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 825c5c2e0962..39d9756a9cef 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -881,7 +881,7 @@ void dqput(struct dquot *dquot)
put_releasing_dquots(dquot);
atomic_dec(&dquot->dq_count);
spin_unlock(&dq_list_lock);
- queue_delayed_work(system_unbound_wq, "a_release_work, 1);
+ queue_delayed_work(system_dfl_wq, "a_release_work, 1);
}
EXPORT_SYMBOL(dqput);
--
2.51.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 2/3] fs: replace use of system_wq with system_percpu_wq
2025-09-05 9:02 [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users Marco Crivellari
2025-09-05 9:02 ` [PATCH 1/3] fs: replace use of system_unbound_wq with system_dfl_wq Marco Crivellari
@ 2025-09-05 9:02 ` Marco Crivellari
2025-09-05 9:02 ` [PATCH 3/3] fs: WQ_PERCPU added to alloc_workqueue users Marco Crivellari
2025-09-15 11:50 ` [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users Christian Brauner
3 siblings, 0 replies; 6+ messages in thread
From: Marco Crivellari @ 2025-09-05 9:02 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: Tejun Heo, Lai Jiangshan, Frederic Weisbecker,
Sebastian Andrzej Siewior, Marco Crivellari, Michal Hocko,
Alexander Viro, Christian Brauner
Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistentcy cannot be addressed without refactoring the API.
system_wq is a per-CPU worqueue, yet nothing in its name tells about that
CPU affinity constraint, which is very often not required by users.
Make it clear by adding a system_percpu_wq to all the fs subsystem.
The old wq will be kept for a few release cylces.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
fs/aio.c | 2 +-
fs/fs-writeback.c | 2 +-
fs/fuse/dev.c | 2 +-
fs/fuse/inode.c | 2 +-
fs/nfs/namespace.c | 2 +-
fs/nfs/nfs4renewd.c | 2 +-
6 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index 7b976b564cfc..747e9b5bba23 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -636,7 +636,7 @@ static void free_ioctx_reqs(struct percpu_ref *ref)
/* Synchronize against RCU protected table->table[] dereferences */
INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
- queue_rcu_work(system_wq, &ctx->free_rwork);
+ queue_rcu_work(system_percpu_wq, &ctx->free_rwork);
}
/*
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index cc57367fb641..cf51a265bf27 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2442,7 +2442,7 @@ static int dirtytime_interval_handler(const struct ctl_table *table, int write,
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (ret == 0 && write)
- mod_delayed_work(system_wq, &dirtytime_work, 0);
+ mod_delayed_work(system_percpu_wq, &dirtytime_work, 0);
return ret;
}
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 6dcbaa218b7a..64b623471a09 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -118,7 +118,7 @@ void fuse_check_timeout(struct work_struct *work)
goto abort_conn;
out:
- queue_delayed_work(system_wq, &fc->timeout.work,
+ queue_delayed_work(system_percpu_wq, &fc->timeout.work,
fuse_timeout_timer_freq);
return;
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index fd48e8d37f2e..6a608ea77d09 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1268,7 +1268,7 @@ static void set_request_timeout(struct fuse_conn *fc, unsigned int timeout)
{
fc->timeout.req_timeout = secs_to_jiffies(timeout);
INIT_DELAYED_WORK(&fc->timeout.work, fuse_check_timeout);
- queue_delayed_work(system_wq, &fc->timeout.work,
+ queue_delayed_work(system_percpu_wq, &fc->timeout.work,
fuse_timeout_timer_freq);
}
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index 973aed9cc5fe..0689369c8a63 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -336,7 +336,7 @@ static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp)
num *= HZ;
*((int *)kp->arg) = num;
if (!list_empty(&nfs_automount_list))
- mod_delayed_work(system_wq, &nfs_automount_task, num);
+ mod_delayed_work(system_percpu_wq, &nfs_automount_task, num);
} else {
*((int *)kp->arg) = -1*HZ;
cancel_delayed_work(&nfs_automount_task);
diff --git a/fs/nfs/nfs4renewd.c b/fs/nfs/nfs4renewd.c
index db3811af0796..18ae614e5a6c 100644
--- a/fs/nfs/nfs4renewd.c
+++ b/fs/nfs/nfs4renewd.c
@@ -122,7 +122,7 @@ nfs4_schedule_state_renewal(struct nfs_client *clp)
timeout = 5 * HZ;
dprintk("%s: requeueing work. Lease period = %ld\n",
__func__, (timeout + HZ - 1) / HZ);
- mod_delayed_work(system_wq, &clp->cl_renewd, timeout);
+ mod_delayed_work(system_percpu_wq, &clp->cl_renewd, timeout);
set_bit(NFS_CS_RENEWD, &clp->cl_res_state);
spin_unlock(&clp->cl_lock);
}
--
2.51.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 3/3] fs: WQ_PERCPU added to alloc_workqueue users
2025-09-05 9:02 [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users Marco Crivellari
2025-09-05 9:02 ` [PATCH 1/3] fs: replace use of system_unbound_wq with system_dfl_wq Marco Crivellari
2025-09-05 9:02 ` [PATCH 2/3] fs: replace use of system_wq with system_percpu_wq Marco Crivellari
@ 2025-09-05 9:02 ` Marco Crivellari
2025-09-15 11:50 ` [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users Christian Brauner
3 siblings, 0 replies; 6+ messages in thread
From: Marco Crivellari @ 2025-09-05 9:02 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: Tejun Heo, Lai Jiangshan, Frederic Weisbecker,
Sebastian Andrzej Siewior, Marco Crivellari, Michal Hocko,
Alexander Viro, Christian Brauner
Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistentcy cannot be addressed without refactoring the API.
alloc_workqueue() treats all queues as per-CPU by default, while unbound
workqueues must opt-in via WQ_UNBOUND.
This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.
This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.
This patch adds a new WQ_PERCPU flag to all the fs subsystem users to
explicitly request the use of the per-CPU behavior. Both flags coexist
for one release cycle to allow callers to transition their calls.
Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.
With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU.
All existing users have been updated accordingly.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
fs/afs/main.c | 4 ++--
fs/bcachefs/super.c | 10 +++++-----
fs/btrfs/async-thread.c | 3 +--
fs/btrfs/disk-io.c | 2 +-
fs/ceph/super.c | 2 +-
fs/dlm/lowcomms.c | 2 +-
fs/dlm/main.c | 2 +-
fs/fs-writeback.c | 2 +-
fs/gfs2/main.c | 5 +++--
fs/gfs2/ops_fstype.c | 6 ++++--
fs/ocfs2/dlm/dlmdomain.c | 3 ++-
fs/ocfs2/dlmfs/dlmfs.c | 3 ++-
fs/smb/client/cifsfs.c | 16 +++++++++++-----
fs/smb/server/ksmbd_work.c | 2 +-
fs/smb/server/transport_rdma.c | 3 ++-
fs/super.c | 3 ++-
fs/verity/verify.c | 2 +-
fs/xfs/xfs_log.c | 3 +--
fs/xfs/xfs_mru_cache.c | 3 ++-
fs/xfs/xfs_super.c | 15 ++++++++-------
20 files changed, 52 insertions(+), 39 deletions(-)
diff --git a/fs/afs/main.c b/fs/afs/main.c
index c845c5daaeba..6b7aab6abd78 100644
--- a/fs/afs/main.c
+++ b/fs/afs/main.c
@@ -168,13 +168,13 @@ static int __init afs_init(void)
printk(KERN_INFO "kAFS: Red Hat AFS client v0.1 registering.\n");
- afs_wq = alloc_workqueue("afs", 0, 0);
+ afs_wq = alloc_workqueue("afs", WQ_PERCPU, 0);
if (!afs_wq)
goto error_afs_wq;
afs_async_calls = alloc_workqueue("kafsd", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
if (!afs_async_calls)
goto error_async;
- afs_lock_manager = alloc_workqueue("kafs_lockd", WQ_MEM_RECLAIM, 0);
+ afs_lock_manager = alloc_workqueue("kafs_lockd", WQ_MEM_RECLAIM | WQ_PERCPU, 0);
if (!afs_lock_manager)
goto error_lockmgr;
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index a58edde43bee..8bba5347a36e 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -909,15 +909,15 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
if (!(c->btree_update_wq = alloc_workqueue("bcachefs",
WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_UNBOUND, 512)) ||
!(c->btree_io_complete_wq = alloc_workqueue("bcachefs_btree_io",
- WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM, 1)) ||
+ WQ_HIGHPRI | WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU, 1)) ||
!(c->copygc_wq = alloc_workqueue("bcachefs_copygc",
- WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 1)) ||
+ WQ_HIGHPRI | WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_CPU_INTENSIVE | WQ_PERCPU, 1)) ||
!(c->btree_read_complete_wq = alloc_workqueue("bcachefs_btree_read_complete",
- WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM, 512)) ||
+ WQ_HIGHPRI | WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU, 512)) ||
!(c->btree_write_submit_wq = alloc_workqueue("bcachefs_btree_write_sumit",
- WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM, 1)) ||
+ WQ_HIGHPRI | WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU, 1)) ||
!(c->write_ref_wq = alloc_workqueue("bcachefs_write_ref",
- WQ_FREEZABLE, 0)) ||
+ WQ_FREEZABLE | WQ_PERCPU, 0)) ||
#ifndef BCH_WRITE_REF_DEBUG
percpu_ref_init(&c->writes, bch2_writes_disabled,
PERCPU_REF_INIT_DEAD, GFP_KERNEL) ||
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index f3bffe08b290..0a84d86a942d 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -109,8 +109,7 @@ struct btrfs_workqueue *btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info,
ret->thresh = thresh;
}
- ret->normal_wq = alloc_workqueue("btrfs-%s", flags, ret->current_active,
- name);
+ ret->normal_wq = alloc_workqueue("btrfs-%s", flags, ret->current_active, name);
if (!ret->normal_wq) {
kfree(ret);
return NULL;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3dd555db3d32..f817b29a43de 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1963,7 +1963,7 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info)
{
u32 max_active = fs_info->thread_pool_size;
unsigned int flags = WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_UNBOUND;
- unsigned int ordered_flags = WQ_MEM_RECLAIM | WQ_FREEZABLE;
+ unsigned int ordered_flags = WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU;
fs_info->workers =
btrfs_alloc_workqueue(fs_info, "worker", flags, max_active, 16);
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index f3951253e393..a0302a004157 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -862,7 +862,7 @@ static struct ceph_fs_client *create_fs_client(struct ceph_mount_options *fsopt,
fsc->inode_wq = alloc_workqueue("ceph-inode", WQ_UNBOUND, 0);
if (!fsc->inode_wq)
goto fail_client;
- fsc->cap_wq = alloc_workqueue("ceph-cap", 0, 1);
+ fsc->cap_wq = alloc_workqueue("ceph-cap", WQ_PERCPU, 1);
if (!fsc->cap_wq)
goto fail_inode_wq;
diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 70abd4da17a6..6ced1fa90209 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -1702,7 +1702,7 @@ static int work_start(void)
return -ENOMEM;
}
- process_workqueue = alloc_workqueue("dlm_process", WQ_HIGHPRI | WQ_BH, 0);
+ process_workqueue = alloc_workqueue("dlm_process", WQ_HIGHPRI | WQ_BH | WQ_PERCPU, 0);
if (!process_workqueue) {
log_print("can't start dlm_process");
destroy_workqueue(io_workqueue);
diff --git a/fs/dlm/main.c b/fs/dlm/main.c
index 4887c8a05318..a44d16da7187 100644
--- a/fs/dlm/main.c
+++ b/fs/dlm/main.c
@@ -52,7 +52,7 @@ static int __init init_dlm(void)
if (error)
goto out_user;
- dlm_wq = alloc_workqueue("dlm_wq", 0, 0);
+ dlm_wq = alloc_workqueue("dlm_wq", WQ_PERCPU, 0);
if (!dlm_wq) {
error = -ENOMEM;
goto out_plock;
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index cf51a265bf27..4b1a53a3266b 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1180,7 +1180,7 @@ void cgroup_writeback_umount(struct super_block *sb)
static int __init cgroup_writeback_init(void)
{
- isw_wq = alloc_workqueue("inode_switch_wbs", 0, 0);
+ isw_wq = alloc_workqueue("inode_switch_wbs", WQ_PERCPU, 0);
if (!isw_wq)
return -ENOMEM;
return 0;
diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
index 0727f60ad028..9d65719353fa 100644
--- a/fs/gfs2/main.c
+++ b/fs/gfs2/main.c
@@ -151,7 +151,8 @@ static int __init init_gfs2_fs(void)
error = -ENOMEM;
gfs2_recovery_wq = alloc_workqueue("gfs2_recovery",
- WQ_MEM_RECLAIM | WQ_FREEZABLE, 0);
+ WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU,
+ 0);
if (!gfs2_recovery_wq)
goto fail_wq1;
@@ -160,7 +161,7 @@ static int __init init_gfs2_fs(void)
if (!gfs2_control_wq)
goto fail_wq2;
- gfs2_freeze_wq = alloc_workqueue("gfs2_freeze", 0, 0);
+ gfs2_freeze_wq = alloc_workqueue("gfs2_freeze", WQ_PERCPU, 0);
if (!gfs2_freeze_wq)
goto fail_wq3;
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index e83d293c3614..0dccb5882ef6 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1189,13 +1189,15 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
error = -ENOMEM;
sdp->sd_glock_wq = alloc_workqueue("gfs2-glock/%s",
- WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_FREEZABLE, 0,
+ WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_FREEZABLE | WQ_PERCPU,
+ 0,
sdp->sd_fsname);
if (!sdp->sd_glock_wq)
goto fail_free;
sdp->sd_delete_wq = alloc_workqueue("gfs2-delete/%s",
- WQ_MEM_RECLAIM | WQ_FREEZABLE, 0, sdp->sd_fsname);
+ WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU, 0,
+ sdp->sd_fsname);
if (!sdp->sd_delete_wq)
goto fail_glock_wq;
diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
index 2018501b2249..2347a50f079b 100644
--- a/fs/ocfs2/dlm/dlmdomain.c
+++ b/fs/ocfs2/dlm/dlmdomain.c
@@ -1876,7 +1876,8 @@ static int dlm_join_domain(struct dlm_ctxt *dlm)
dlm_debug_init(dlm);
snprintf(wq_name, O2NM_MAX_NAME_LEN, "dlm_wq-%s", dlm->name);
- dlm->dlm_worker = alloc_workqueue(wq_name, WQ_MEM_RECLAIM, 0);
+ dlm->dlm_worker = alloc_workqueue(wq_name, WQ_MEM_RECLAIM | WQ_PERCPU,
+ 0);
if (!dlm->dlm_worker) {
status = -ENOMEM;
mlog_errno(status);
diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index 5130ec44e5e1..0b730535b2c8 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -595,7 +595,8 @@ static int __init init_dlmfs_fs(void)
}
cleanup_inode = 1;
- user_dlm_worker = alloc_workqueue("user_dlm", WQ_MEM_RECLAIM, 0);
+ user_dlm_worker = alloc_workqueue("user_dlm",
+ WQ_MEM_RECLAIM | WQ_PERCPU, 0);
if (!user_dlm_worker) {
status = -ENOMEM;
goto bail;
diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index a08c42363ffc..3d3a76fa7210 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -1883,7 +1883,9 @@ init_cifs(void)
cifs_dbg(VFS, "dir_cache_timeout set to max of 65000 seconds\n");
}
- cifsiod_wq = alloc_workqueue("cifsiod", WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+ cifsiod_wq = alloc_workqueue("cifsiod",
+ WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+ 0);
if (!cifsiod_wq) {
rc = -ENOMEM;
goto out_clean_proc;
@@ -1911,28 +1913,32 @@ init_cifs(void)
}
cifsoplockd_wq = alloc_workqueue("cifsoplockd",
- WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+ WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+ 0);
if (!cifsoplockd_wq) {
rc = -ENOMEM;
goto out_destroy_fileinfo_put_wq;
}
deferredclose_wq = alloc_workqueue("deferredclose",
- WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+ WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+ 0);
if (!deferredclose_wq) {
rc = -ENOMEM;
goto out_destroy_cifsoplockd_wq;
}
serverclose_wq = alloc_workqueue("serverclose",
- WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+ WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+ 0);
if (!serverclose_wq) {
rc = -ENOMEM;
goto out_destroy_deferredclose_wq;
}
cfid_put_wq = alloc_workqueue("cfid_put_wq",
- WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+ WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+ 0);
if (!cfid_put_wq) {
rc = -ENOMEM;
goto out_destroy_serverclose_wq;
diff --git a/fs/smb/server/ksmbd_work.c b/fs/smb/server/ksmbd_work.c
index 72b00ca6e455..4a71f46d7020 100644
--- a/fs/smb/server/ksmbd_work.c
+++ b/fs/smb/server/ksmbd_work.c
@@ -78,7 +78,7 @@ int ksmbd_work_pool_init(void)
int ksmbd_workqueue_init(void)
{
- ksmbd_wq = alloc_workqueue("ksmbd-io", 0, 0);
+ ksmbd_wq = alloc_workqueue("ksmbd-io", WQ_PERCPU, 0);
if (!ksmbd_wq)
return -ENOMEM;
return 0;
diff --git a/fs/smb/server/transport_rdma.c b/fs/smb/server/transport_rdma.c
index 4998df04ab95..43b7062335fa 100644
--- a/fs/smb/server/transport_rdma.c
+++ b/fs/smb/server/transport_rdma.c
@@ -2198,7 +2198,8 @@ int ksmbd_rdma_init(void)
* for lack of credits
*/
smb_direct_wq = alloc_workqueue("ksmbd-smb_direct-wq",
- WQ_HIGHPRI | WQ_MEM_RECLAIM, 0);
+ WQ_HIGHPRI | WQ_MEM_RECLAIM | WQ_PERCPU,
+ 0);
if (!smb_direct_wq)
return -ENOMEM;
diff --git a/fs/super.c b/fs/super.c
index 97a17f9d9023..0a9af48f30dd 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -2174,7 +2174,8 @@ int sb_init_dio_done_wq(struct super_block *sb)
{
struct workqueue_struct *old;
struct workqueue_struct *wq = alloc_workqueue("dio/%s",
- WQ_MEM_RECLAIM, 0,
+ WQ_MEM_RECLAIM | WQ_PERCPU,
+ 0,
sb->s_id);
if (!wq)
return -ENOMEM;
diff --git a/fs/verity/verify.c b/fs/verity/verify.c
index 4fcad0825a12..b8f53d1cfd20 100644
--- a/fs/verity/verify.c
+++ b/fs/verity/verify.c
@@ -357,7 +357,7 @@ void __init fsverity_init_workqueue(void)
* latency on ARM64.
*/
fsverity_read_workqueue = alloc_workqueue("fsverity_read_queue",
- WQ_HIGHPRI,
+ WQ_HIGHPRI | WQ_PERCPU,
num_online_cpus());
if (!fsverity_read_workqueue)
panic("failed to allocate fsverity_read_queue");
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 6493bdb57351..3fecb066eeb3 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1489,8 +1489,7 @@ xlog_alloc_log(
log->l_iclog->ic_prev = prev_iclog; /* re-write 1st prev ptr */
log->l_ioend_workqueue = alloc_workqueue("xfs-log/%s",
- XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM |
- WQ_HIGHPRI),
+ XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_PERCPU),
0, mp->m_super->s_id);
if (!log->l_ioend_workqueue)
goto out_free_iclog;
diff --git a/fs/xfs/xfs_mru_cache.c b/fs/xfs/xfs_mru_cache.c
index d0f5b403bdbe..152032f68013 100644
--- a/fs/xfs/xfs_mru_cache.c
+++ b/fs/xfs/xfs_mru_cache.c
@@ -293,7 +293,8 @@ int
xfs_mru_cache_init(void)
{
xfs_mru_reap_wq = alloc_workqueue("xfs_mru_cache",
- XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE), 1);
+ XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU),
+ 1);
if (!xfs_mru_reap_wq)
return -ENOMEM;
return 0;
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index b2dd0c0bf509..38584c5618f4 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -565,19 +565,19 @@ xfs_init_mount_workqueues(
struct xfs_mount *mp)
{
mp->m_buf_workqueue = alloc_workqueue("xfs-buf/%s",
- XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
+ XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU),
1, mp->m_super->s_id);
if (!mp->m_buf_workqueue)
goto out;
mp->m_unwritten_workqueue = alloc_workqueue("xfs-conv/%s",
- XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
+ XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU),
0, mp->m_super->s_id);
if (!mp->m_unwritten_workqueue)
goto out_destroy_buf;
mp->m_reclaim_workqueue = alloc_workqueue("xfs-reclaim/%s",
- XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
+ XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU),
0, mp->m_super->s_id);
if (!mp->m_reclaim_workqueue)
goto out_destroy_unwritten;
@@ -589,13 +589,14 @@ xfs_init_mount_workqueues(
goto out_destroy_reclaim;
mp->m_inodegc_wq = alloc_workqueue("xfs-inodegc/%s",
- XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
+ XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU),
1, mp->m_super->s_id);
if (!mp->m_inodegc_wq)
goto out_destroy_blockgc;
mp->m_sync_workqueue = alloc_workqueue("xfs-sync/%s",
- XFS_WQFLAGS(WQ_FREEZABLE), 0, mp->m_super->s_id);
+ XFS_WQFLAGS(WQ_FREEZABLE | WQ_PERCPU), 0,
+ mp->m_super->s_id);
if (!mp->m_sync_workqueue)
goto out_destroy_inodegc;
@@ -2499,8 +2500,8 @@ xfs_init_workqueues(void)
* AGs in all the filesystems mounted. Hence use the default large
* max_active value for this workqueue.
*/
- xfs_alloc_wq = alloc_workqueue("xfsalloc",
- XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE), 0);
+ xfs_alloc_wq = alloc_workqueue("xfsalloc", XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU),
+ 0);
if (!xfs_alloc_wq)
return -ENOMEM;
--
2.51.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users
2025-09-05 9:02 [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users Marco Crivellari
` (2 preceding siblings ...)
2025-09-05 9:02 ` [PATCH 3/3] fs: WQ_PERCPU added to alloc_workqueue users Marco Crivellari
@ 2025-09-15 11:50 ` Christian Brauner
2025-09-15 12:20 ` Marco Crivellari
3 siblings, 1 reply; 6+ messages in thread
From: Christian Brauner @ 2025-09-15 11:50 UTC (permalink / raw)
To: Marco Crivellari
Cc: linux-kernel, linux-fsdevel, Tejun Heo, Lai Jiangshan,
Frederic Weisbecker, Sebastian Andrzej Siewior, Michal Hocko,
Alexander Viro
On Fri, Sep 05, 2025 at 11:02:11AM +0200, Marco Crivellari wrote:
> Hi!
>
> Below is a summary of a discussion about the Workqueue API and cpu isolation
> considerations. Details and more information are available here:
>
> "workqueue: Always use wq_select_unbound_cpu() for WORK_CPU_UNBOUND."
> https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/
>
> === Current situation: problems ===
>
> Let's consider a nohz_full system with isolated CPUs: wq_unbound_cpumask is
> set to the housekeeping CPUs, for !WQ_UNBOUND the local CPU is selected.
>
> This leads to different scenarios if a work item is scheduled on an isolated
> CPU where "delay" value is 0 or greater then 0:
> schedule_delayed_work(, 0);
>
> This will be handled by __queue_work() that will queue the work item on the
> current local (isolated) CPU, while:
>
> schedule_delayed_work(, 1);
>
> Will move the timer on an housekeeping CPU, and schedule the work there.
>
> Currently if a user enqueue a work item using schedule_delayed_work() the
> used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
> WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
> schedule_work() that is using system_wq and queue_work(), that makes use
> again of WORK_CPU_UNBOUND.
>
> This lack of consistentcy cannot be addressed without refactoring the API.
>
> === Plan and future plans ===
>
> This patchset is the first stone on a refactoring needed in order to
> address the points aforementioned; it will have a positive impact also
> on the cpu isolation, in the long term, moving away percpu workqueue in
> favor to an unbound model.
>
> These are the main steps:
> 1) API refactoring (that this patch is introducing)
> - Make more clear and uniform the system wq names, both per-cpu and
> unbound. This to avoid any possible confusion on what should be
> used.
>
> - Introduction of WQ_PERCPU: this flag is the complement of WQ_UNBOUND,
> introduced in this patchset and used on all the callers that are not
> currently using WQ_UNBOUND.
>
> WQ_UNBOUND will be removed in a future release cycle.
>
> Most users don't need to be per-cpu, because they don't have
> locality requirements, because of that, a next future step will be
> make "unbound" the default behavior.
>
> 2) Check who really needs to be per-cpu
> - Remove the WQ_PERCPU flag when is not strictly required.
>
> 3) Add a new API (prefer local cpu)
> - There are users that don't require a local execution, like mentioned
> above; despite that, local execution yeld to performance gain.
>
> This new API will prefer the local execution, without requiring it.
>
> === Introduced Changes by this series ===
>
> 1) [P 1-2] Replace use of system_wq and system_unbound_wq
>
> system_wq is a per-CPU workqueue, but his name is not clear.
> system_unbound_wq is to be used when locality is not required.
>
> Because of that, system_wq has been renamed in system_percpu_wq, and
> system_unbound_wq has been renamed in system_dfl_wq.
>
> 2) [P 3] add WQ_PERCPU to remaining alloc_workqueue() users
>
> Every alloc_workqueue() caller should use one among WQ_PERCPU or
> WQ_UNBOUND. This is actually enforced warning if both or none of them
> are present at the same time.
>
> WQ_UNBOUND will be removed in a next release cycle.
>
> === For Maintainers ===
>
> There are prerequisites for this series, already merged in the master branch.
> The commits are:
>
> 128ea9f6ccfb6960293ae4212f4f97165e42222d ("workqueue: Add system_percpu_wq and
> system_dfl_wq")
>
> 930c2ea566aff59e962c50b2421d5fcc3b98b8be ("workqueue: Add new WQ_PERCPU flag")
What is this based on? This doesn't apply to any v6.17-rc* tag so I
can't merge it.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users
2025-09-15 11:50 ` [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users Christian Brauner
@ 2025-09-15 12:20 ` Marco Crivellari
0 siblings, 0 replies; 6+ messages in thread
From: Marco Crivellari @ 2025-09-15 12:20 UTC (permalink / raw)
To: Christian Brauner
Cc: linux-kernel, linux-fsdevel, Tejun Heo, Lai Jiangshan,
Frederic Weisbecker, Sebastian Andrzej Siewior, Michal Hocko,
Alexander Viro
On Mon, Sep 15, 2025 at 1:50 PM Christian Brauner <brauner@kernel.org> wrote:
> What is this based on? This doesn't apply to any v6.17-rc* tag so I
> can't merge it.
Sorry Christian, it is still based on an older version. I will rebase
and repost.
Thanks!
--
Marco Crivellari
L3 Support Engineer, Technology & Product
marco.crivellari@suse.com
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2025-09-15 12:20 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2025-09-05 9:02 [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users Marco Crivellari
2025-09-05 9:02 ` [PATCH 1/3] fs: replace use of system_unbound_wq with system_dfl_wq Marco Crivellari
2025-09-05 9:02 ` [PATCH 2/3] fs: replace use of system_wq with system_percpu_wq Marco Crivellari
2025-09-05 9:02 ` [PATCH 3/3] fs: WQ_PERCPU added to alloc_workqueue users Marco Crivellari
2025-09-15 11:50 ` [PATCH 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users Christian Brauner
2025-09-15 12:20 ` Marco Crivellari
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