[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-Id: <20070320181235.77d28864.dada1@cosmosbay.com>
Date: Tue, 20 Mar 2007 18:12:35 +0100
From: Eric Dumazet <dada1@...mosbay.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Christoph Lameter <christoph@...eter.com>,
Andi Kleen <andi@...stfloor.org>
Cc: linux kernel <linux-kernel@...r.kernel.org>
Subject: [RFC] SLAB : NUMA cache_free_alien() very expensive because of
virt_to_slab(objp); nodeid = slabp->nodeid;
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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists