From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <47AC04CD.9090407@cosmosbay.com> Date: Fri, 08 Feb 2008 08:29:17 +0100 From: Eric Dumazet MIME-Version: 1.0 Subject: Re: [git pull] more SLUB updates for 2.6.25 References: <200802081812.22513.nickpiggin@yahoo.com.au> In-Reply-To: <200802081812.22513.nickpiggin@yahoo.com.au> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Christoph Lameter , Linus Torvalds , Andrew Morton , LKML , linux-mm@kvack.org List-ID: Nick Piggin a ecrit : > On Friday 08 February 2008 13:13, Christoph Lameter wrote: >> are available in the git repository at: >> >> git://git.kernel.org/pub/scm/linux/kernel/git/christoph/vm.git slub-linus >> >> (includes the cmpxchg_local fastpath since the cmpxchg_local work >> by Matheiu is in now, and the non atomic unlock by Nick. Verified that >> this is not doing any harm after some other patches had been removed. > > Ah, good. I think it is always a good thing to be able to remove atomics. > They place quite a bit of burden on the CPU, especially x86 where it also > has implicit memory ordering semantics (although x86 can speculatively > get around much of the problem, it's obviously worse than no restriction) > > Even if perhaps some cache coherency or timing quirk makes the non-atomic > version slower (all else being equal), then I'd still say that the non > atomic version should be preferred. > What about IRQ masking then ? Many CPU pay high cost for cli/sti pair... And SLAB/SLUB allocators, even if only used from process context, want to disable/re-enable interrupts... I understand kmalloc() want generic pools, but dedicated pools could avoid this cli/sti -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org