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Message-ID: <20080307031044.GF21185@wotan.suse.de> Date: Fri, 7 Mar 2008 04:10:44 +0100 From: Nick Piggin <npiggin@...e.de> To: Christoph Lameter <clameter@....com> Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, yanmin_zhang@...ux.intel.com, dada1@...mosbay.com Subject: Re: [rfc][patch 1/3] slub: fix small HWCACHE_ALIGN alignment On Thu, Mar 06, 2008 at 06:54:19PM -0800, Christoph Lameter wrote: > > It doesn't say start of cache line. It says align them *on* cachelines. > > 2 32 byte objects on a 64 byte cacheline are aligned on the cacheline. > > 2.67 24 bytes objects on a 64 byte cacheline are not aligned on the > > cacheline. > > 2 32 byte objects means only one is aligned on a cache line. > > Certainly cacheline contention is reduced and performance potentially > increased if there are less objects in a cacheline. > > The same argument can be made of aligning 8 byte objects on 32 byte > boundaries. Instead of 8 objects per cacheline you only have two. Why 8? > > Isnt all of this a bit arbitrary and contrary to the intend of avoiding > cacheline contention? No, it *is not about avoiding cacheline contention*. As such, the rest of what you wrote below about smp_align etc is rubbish. Can you actually read what I posted? -- 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/
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