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Date: Fri, 14 Aug 2009 10:58:41 +0200 From: Nick Piggin <npiggin@...e.de> To: Manfred Spraul <manfred@...orfullife.com> Cc: Zach Brown <zach.brown@...cle.com>, Andrew Morton <akpm@...ux-foundation.org>, Nadia Derbey <Nadia.Derbey@...l.net>, Pierre Peiffer <peifferp@...il.com>, linux-kernel@...r.kernel.org Subject: Re: [patch 4/4] ipc: sem optimise simple operations On Wed, Aug 12, 2009 at 08:35:56PM +0200, Manfred Spraul wrote: > On 08/12/2009 06:07 AM, Nick Piggin wrote: > >A semaphore set with 250 will use 2K before, and 10K afterward. I > >don't know that it is a huge amount really, given that they also > >have to presumably be *protecting* stuff. > > > > > The allocation uses vmalloc for larger allocations, thus 10k should not > be an issue. > >We can convert them to hlists (I was going to send a patch to do > >everything in hlists, but hlists are missing some _rcu variants... > >maybe I should just convert the pending lists to start with). > > > > > Is it possible to use list_add and list_add_tail instead? > Add the "waiting for zero" to the beginning and "waiting for nonzero" to > the end. The only problem with this is that it means we have to walk through the list of wait-for-zero for every increment operation, before getting to the list of negative ops. The wait-for-zero list should be empty in the case of simple modify operations which are strictly +1/-1 I guess though. I do like how it cleanly splits the modify and non-modify operations though. But if you feel strongly about saving the sapce, I will do as you suggest. Thanks, Nick -- 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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