From: Xiubo Li via B4 Relay <devnull+xiubo.li.clyso.com@kernel.org>
To: Ilya Dryomov <idryomov@gmail.com>,
Alex Markuze <amarkuze@redhat.com>,
Viacheslav Dubeyko <slava@dubeyko.com>
Cc: ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org,
Xiubo Li <xiubo.li@clyso.com>
Subject: [PATCH v3 4/5] ceph: move mdsc->mutex into __do_request()
Date: Tue, 11 Aug 2026 13:17:48 +0800 [thread overview]
Message-ID: <20260811-ceph-mdsc-mutex-optimization-v3-4-d031114419f4@clyso.com> (raw)
In-Reply-To: <20260811-ceph-mdsc-mutex-optimization-v3-0-d031114419f4@clyso.com>
From: Xiubo Li <xiubo.li@clyso.com>
Currently every caller must hold mdsc->mutex when invoking the
request-send machinery. Move the mutex acquisition inside
__do_request() so that callers can fire off a request without
first serializing on the global lock. The mutex is released
before the network send phase and re-acquired only for cleanup,
so dentry traversal and message construction run concurrently
across CPUs.
This is the primary source of the observed 2x stat throughput
improvement: the per-request send path shrinks from hundreds of
microseconds to tens of microseconds once it no longer waits on
the mutex. Wait-list draining, session-state wake-ups, and
request kicking are reworked to either use the new wait-list
spinlock or collect candidates under the mutex and process them
outside it.
Signed-off-by: Xiubo Li <xiubo.li@clyso.com>
---
fs/ceph/mds_client.c | 69 ++++++++++++++++++++++++++++++++--------------------
1 file changed, 42 insertions(+), 27 deletions(-)
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 2d2994b4399b..76dfd2c86392 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3586,9 +3586,12 @@ static void __do_request(struct ceph_mds_client *mdsc,
int err = 0;
bool random;
+ mutex_lock(&mdsc->mutex);
+
if (req->r_err || test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags)) {
if (test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags))
__unregister_request(mdsc, req);
+ mutex_unlock(&mdsc->mutex);
return;
}
@@ -3621,6 +3624,7 @@ static void __do_request(struct ceph_mds_client *mdsc,
spin_lock(&mdsc->wait_list_lock);
list_add(&req->r_wait, &mdsc->waiting_for_map);
spin_unlock(&mdsc->wait_list_lock);
+ mutex_unlock(&mdsc->mutex);
return;
}
if (!(mdsc->fsc->mount_options->flags &
@@ -3646,6 +3650,7 @@ static void __do_request(struct ceph_mds_client *mdsc,
spin_lock(&mdsc->wait_list_lock);
list_add(&req->r_wait, &mdsc->waiting_for_map);
spin_unlock(&mdsc->wait_list_lock);
+ mutex_unlock(&mdsc->mutex);
return;
}
@@ -3719,6 +3724,8 @@ static void __do_request(struct ceph_mds_client *mdsc,
goto out_session;
}
+ mutex_unlock(&mdsc->mutex);
+
/* send request */
req->r_resend_mds = -1; /* forget any previous mds hint */
@@ -3749,6 +3756,7 @@ static void __do_request(struct ceph_mds_client *mdsc,
err = wait_on_bit(&di->flags, CEPH_DENTRY_ASYNC_CREATE_BIT,
TASK_KILLABLE);
if (err) {
+ mutex_lock(&mdsc->mutex);
mutex_lock(&req->r_fill_mutex);
set_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags);
mutex_unlock(&req->r_fill_mutex);
@@ -3786,6 +3794,8 @@ static void __do_request(struct ceph_mds_client *mdsc,
err = __send_request(session, req, false);
+ mutex_lock(&mdsc->mutex);
+
out_session:
ceph_put_mds_session(session);
finish:
@@ -3795,12 +3805,10 @@ static void __do_request(struct ceph_mds_client *mdsc,
complete_request(mdsc, req);
__unregister_request(mdsc, req);
}
+ mutex_unlock(&mdsc->mutex);
return;
}
-/*
- * called under mdsc->mutex
- */
static void __wake_requests(struct ceph_mds_client *mdsc,
struct list_head *head)
{
@@ -3830,10 +3838,14 @@ static void __wake_requests(struct ceph_mds_client *mdsc,
static void kick_requests(struct ceph_mds_client *mdsc, int mds)
{
struct ceph_client *cl = mdsc->fsc->client;
- struct ceph_mds_request *req;
+ struct ceph_mds_request *req, *nreq;
unsigned long idx;
+ LIST_HEAD(kick_list);
doutc(cl, "kick_requests mds%d\n", mds);
+
+ /* collect matching requests under the mutex */
+ mutex_lock(&mdsc->mutex);
idx = 0;
xa_for_each(&mdsc->request_tree, idx, req) {
if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
@@ -3842,14 +3854,23 @@ static void kick_requests(struct ceph_mds_client *mdsc, int mds)
continue; /* only new requests */
if (req->r_session &&
req->r_session->s_mds == mds) {
- doutc(cl, " kicking tid %llu\n", req->r_tid);
+ ceph_mdsc_get_request(req);
spin_lock(&mdsc->wait_list_lock);
list_del_init(&req->r_wait);
spin_unlock(&mdsc->wait_list_lock);
- trace_ceph_mdsc_resume_request(mdsc, req);
- __do_request(mdsc, req);
+ list_add_tail(&req->r_wait, &kick_list);
}
}
+ mutex_unlock(&mdsc->mutex);
+
+ /* replay without the mutex */
+ list_for_each_entry_safe(req, nreq, &kick_list, r_wait) {
+ doutc(cl, " kicking tid %llu\n", req->r_tid);
+ trace_ceph_mdsc_resume_request(mdsc, req);
+ __do_request(mdsc, req);
+ list_del_init(&req->r_wait);
+ ceph_mdsc_put_request(req);
+ }
}
int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir,
@@ -3909,10 +3930,11 @@ int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir,
doutc(cl, "submit_request on %p for inode %p\n", req, dir);
mutex_lock(&mdsc->mutex);
__register_request(mdsc, req, dir);
+ mutex_unlock(&mdsc->mutex);
+
trace_ceph_mdsc_submit_request(mdsc, req);
__do_request(mdsc, req);
err = req->r_err;
- mutex_unlock(&mdsc->mutex);
return err;
}
@@ -4295,13 +4317,14 @@ static void handle_forward(struct ceph_mds_client *mdsc,
req->r_num_fwd = fwd_seq;
req->r_resend_mds = next_mds;
put_request_session(req);
- __do_request(mdsc, req);
}
mutex_unlock(&mdsc->mutex);
/* kick calling process */
if (aborted)
complete_request(mdsc, req);
+ else if (!test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags))
+ __do_request(mdsc, req);
ceph_mdsc_put_request(req);
return;
@@ -4625,11 +4648,9 @@ static void handle_session(struct ceph_mds_session *session,
mutex_unlock(&session->s_mutex);
if (wake) {
- mutex_lock(&mdsc->mutex);
__wake_requests(mdsc, &session->s_waiting);
if (wake == 2)
kick_requests(mdsc, mds);
- mutex_unlock(&mdsc->mutex);
}
if (op == CEPH_SESSION_CLOSE)
ceph_put_mds_session(session);
@@ -5264,9 +5285,7 @@ static int send_mds_reconnect(struct ceph_mds_client *mdsc,
mutex_unlock(&session->s_mutex);
- mutex_lock(&mdsc->mutex);
__wake_requests(mdsc, &session->s_waiting);
- mutex_unlock(&mdsc->mutex);
up_read(&mdsc->snap_rwsem);
ceph_pagelist_release(recon_state.pagelist);
@@ -5691,8 +5710,8 @@ static void ceph_mdsc_reset_workfn(struct work_struct *work)
}
sessions[i]->s_state = CEPH_MDS_SESSION_CLOSED;
__unregister_session(mdsc, sessions[i]);
- __wake_requests(mdsc, &sessions[i]->s_waiting);
mutex_unlock(&mdsc->mutex);
+ __wake_requests(mdsc, &sessions[i]->s_waiting);
mutex_lock(&sessions[i]->s_mutex);
cleanup_session_requests(mdsc, sessions[i]);
@@ -5703,9 +5722,7 @@ static void ceph_mdsc_reset_workfn(struct work_struct *work)
ceph_put_mds_session(sessions[i]);
- mutex_lock(&mdsc->mutex);
kick_requests(mdsc, mds);
- mutex_unlock(&mdsc->mutex);
torn_down++;
pr_info_client(cl, "mds%d session reset complete\n", mds);
@@ -5821,8 +5838,8 @@ static void check_new_map(struct ceph_mds_client *mdsc,
/* force close session for stopped mds */
ceph_get_mds_session(s);
__unregister_session(mdsc, s);
- __wake_requests(mdsc, &s->s_waiting);
mutex_unlock(&mdsc->mutex);
+ __wake_requests(mdsc, &s->s_waiting);
mutex_lock(&s->s_mutex);
cleanup_session_requests(mdsc, s);
@@ -5831,8 +5848,8 @@ static void check_new_map(struct ceph_mds_client *mdsc,
ceph_put_mds_session(s);
- mutex_lock(&mdsc->mutex);
kick_requests(mdsc, i);
+ mutex_lock(&mdsc->mutex);
continue;
}
@@ -5876,8 +5893,8 @@ static void check_new_map(struct ceph_mds_client *mdsc,
oldstate != CEPH_MDS_STATE_STARTING)
pr_info_client(cl, "mds%d recovery completed\n",
s->s_mds);
- kick_requests(mdsc, i);
mutex_unlock(&mdsc->mutex);
+ kick_requests(mdsc, i);
mutex_lock(&s->s_mutex);
mutex_lock(&mdsc->mutex);
ceph_kick_flushing_caps(mdsc, s);
@@ -6785,8 +6802,8 @@ void ceph_mdsc_force_umount(struct ceph_mds_client *mdsc)
if (session->s_state == CEPH_MDS_SESSION_REJECTED)
__unregister_session(mdsc, session);
- __wake_requests(mdsc, &session->s_waiting);
mutex_unlock(&mdsc->mutex);
+ __wake_requests(mdsc, &session->s_waiting);
mutex_lock(&session->s_mutex);
__close_session(mdsc, session);
@@ -6797,11 +6814,11 @@ void ceph_mdsc_force_umount(struct ceph_mds_client *mdsc)
mutex_unlock(&session->s_mutex);
ceph_put_mds_session(session);
- mutex_lock(&mdsc->mutex);
kick_requests(mdsc, mds);
+ mutex_lock(&mdsc->mutex);
}
- __wake_requests(mdsc, &mdsc->waiting_for_map);
mutex_unlock(&mdsc->mutex);
+ __wake_requests(mdsc, &mdsc->waiting_for_map);
}
static void ceph_mdsc_stop(struct ceph_mds_client *mdsc)
@@ -6943,8 +6960,8 @@ void ceph_mdsc_handle_fsmap(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
err_out:
mutex_lock(&mdsc->mutex);
mdsc->mdsmap_err = err;
- __wake_requests(mdsc, &mdsc->waiting_for_map);
mutex_unlock(&mdsc->mutex);
+ __wake_requests(mdsc, &mdsc->waiting_for_map);
}
/*
@@ -6995,11 +7012,11 @@ void ceph_mdsc_handle_mdsmap(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
mdsc->fsc->max_file_size = min((loff_t)mdsc->mdsmap->m_max_file_size,
MAX_LFS_FILESIZE);
+ mutex_unlock(&mdsc->mutex);
__wake_requests(mdsc, &mdsc->waiting_for_map);
ceph_monc_got_map(&mdsc->fsc->client->monc, CEPH_SUB_MDSMAP,
mdsc->mdsmap->m_epoch);
- mutex_unlock(&mdsc->mutex);
schedule_delayed(mdsc, 0);
return;
@@ -7097,8 +7114,8 @@ static void mds_peer_reset(struct ceph_connection *con)
ceph_get_mds_session(s);
s->s_state = CEPH_MDS_SESSION_CLOSED;
__unregister_session(mdsc, s);
- __wake_requests(mdsc, &s->s_waiting);
mutex_unlock(&mdsc->mutex);
+ __wake_requests(mdsc, &s->s_waiting);
mutex_lock(&s->s_mutex);
cleanup_session_requests(mdsc, s);
@@ -7107,9 +7124,7 @@ static void mds_peer_reset(struct ceph_connection *con)
wake_up_all(&mdsc->session_close_wq);
- mutex_lock(&mdsc->mutex);
kick_requests(mdsc, s->s_mds);
- mutex_unlock(&mdsc->mutex);
ceph_put_mds_session(s);
break;
--
2.53.0
next prev parent reply other threads:[~2026-08-11 5:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-11 5:17 [PATCH v3 0/5] ceph: reduce mdsc->mutex contention in the cephfs kclient Xiubo Li via B4 Relay
2026-08-11 5:17 ` [PATCH v3 1/5] ceph: use READ_ONCE/WRITE_ONCE for oldest_tid Xiubo Li via B4 Relay
2026-08-11 5:17 ` [PATCH v3 2/5] ceph: replace the request_tree rbtree with an xarray keyed by r_tid Xiubo Li via B4 Relay
2026-08-11 5:17 ` [PATCH v3 3/5] ceph: add wait_list_lock for wait-list serialization Xiubo Li via B4 Relay
2026-08-11 5:17 ` Xiubo Li via B4 Relay [this message]
2026-08-11 5:17 ` [PATCH v3 5/5] ceph: narrow mdsc->mutex scope in replay_unsafe_requests Xiubo Li via B4 Relay
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260811-ceph-mdsc-mutex-optimization-v3-4-d031114419f4@clyso.com \
--to=devnull+xiubo.li.clyso.com@kernel.org \
--cc=amarkuze@redhat.com \
--cc=ceph-devel@vger.kernel.org \
--cc=idryomov@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=slava@dubeyko.com \
--cc=xiubo.li@clyso.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®