lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 30 Nov 2007 11:14:01 +0200 (EET) From: Pekka J Enberg <penberg@...helsinki.fi> To: Andrew Morton <akpm@...ux-foundation.org> cc: Matthew Wilcox <matthew@....cx>, Linus Torvalds <torvalds@...ux-foundation.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCH] Fix kmem_cache_free performance regression in slab Hi, On Thu, 29 Nov 2007 12:05:13 -0700 Matthew Wilcox <matthew@....cx> wrote: > > The database performance group have found that half the cycles spent > > in kmem_cache_free are spent in this one call to BUG_ON. Moving it > > into the CONFIG_SLAB_DEBUG-only function cache_free_debugcheck() is a > > performance win of almost 0.5% on their particular benchmark. > > > > The call was added as part of commit ddc2e812d592457747c4367fb73edcaa8e1e49ff > > with the comment that "overhead should be minimal". It may have been > > minimal at the time, but it isn't now. > > On Thu, 29 Nov 2007, Andrew Morton wrote: > It is worth noting that the offending commit hit mainline in June 2006. > > It takes a very long time for some performance regressions to be > discovered. By which time it is effectively too late to fix it. What architecture is this? x86_64? I don't think the BUG_ON per se caused the performance regression but rather the virt_to_head_page() changes to virt_to_cache() that were added later. But reverting the BUG_ON is fine by me. Thanks Matthew and others for tracking this down! Pekka - 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