From: Eric Dumazet <dada1@cosmosbay.com>
To: Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <christoph@lameter.com>,
Andi Kleen <andi@firstfloor.org>
Cc: linux kernel <linux-kernel@vger.kernel.org>
Subject: [RFC] SLAB : NUMA cache_free_alien() very expensive because of virt_to_slab(objp); nodeid = slabp->nodeid;
Date: Tue, 20 Mar 2007 18:12:35 +0100 [thread overview]
Message-ID: <20070320181235.77d28864.dada1@cosmosbay.com> (raw)
Hi
I noticed on a small x86_64 NUMA setup (2 nodes) that cache_free_alien() is very expensive.
This is because of a cache miss on struct slab.
At the time an object is freed (call to kmem_cache_free() for example), the underlying 'struct slab' is not anymore cache-hot.
struct slab *slabp = virt_to_slab(objp);
nodeid = slabp->nodeid; // cache miss
So we currently need slab only to lookup nodeid, to be able to use the cachep cpu cache, or not.
Couldn't we use something less expensive, like pfn_to_nid() ?
On x86_64 pfn_to_nid usually shares one cache line for all objects (struct memnode)
Is it possible virt_to_slab(objp)->nodeid being different from pfn_to_nid(objp) ?
Eric
next reply other threads:[~2007-03-20 17:12 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-20 17:12 Eric Dumazet [this message]
2007-03-20 19:54 ` Christoph Lameter
2007-03-20 21:32 ` Andi Kleen
2007-03-20 22:09 ` Eric Dumazet
2007-03-21 0:16 ` Christoph Lameter
2007-03-21 6:27 ` Eric Dumazet
2007-03-21 6:57 ` [PATCH] SLAB : Use num_possible_cpus() in enable_cpucache() Eric Dumazet
2007-03-21 7:21 ` [PATCH] SLAB : Dont allocate empty shared caches Eric Dumazet
2007-03-21 13:13 ` Pekka Enberg
2007-03-21 13:02 ` [PATCH] SLAB : Use num_possible_cpus() in enable_cpucache() Pekka Enberg
2007-03-21 18:45 ` Christoph Lameter
2007-03-21 7:03 ` [RFC] SLAB : NUMA cache_free_alien() very expensive because of virt_to_slab(objp); nodeid = slabp->nodeid; Christoph Lameter
2007-03-21 7:14 ` Eric Dumazet
2007-03-21 14:35 ` Christoph Lameter
2007-03-21 0:18 ` Christoph Lameter
2007-03-21 2:44 ` Andi Kleen
2007-03-21 3:10 ` Christoph Lameter
2007-03-22 21:28 ` non-NUMA cache_free_alien() (was Re: [RFC] SLAB : NUMA cache_free_alien() very expensive because of virt_to_slab(objp); nodeid = slabp->nodeid;) Siddha, Suresh B
2007-03-22 22:10 ` Christoph Lameter
2007-03-22 22:12 ` Eric Dumazet
2007-03-22 22:40 ` Siddha, Suresh B
2007-03-22 22:56 ` Eric Dumazet
2007-03-23 1:25 ` Christoph Lameter
2007-03-23 14:14 ` Andi Kleen
2007-03-23 14:12 ` Andi Kleen
2007-04-02 22:55 ` Siddha, Suresh B
2007-04-03 0:23 ` Christoph Lameter
2007-04-03 0:31 ` Siddha, Suresh B
2007-04-09 18:01 ` [patch 1/2] x86_64: set node_possible_map at runtime Siddha, Suresh B
2007-04-09 18:07 ` [patch 2/2] slab, x86_64: skip cache_free_alien() on non NUMA Siddha, Suresh B
2007-04-09 20:23 ` [patch 1/2] x86_64: set node_possible_map at runtime Andrew Morton
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