From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from edge01.upc.biz ([192.168.13.236]) by viefep15-int.chello.at (InterMail vM.7.08.02.00 201-2186-121-20061213) with ESMTP id <20080728171350.KEZM14014.viefep15-int.chello.at@edge01.upc.biz> for ; Mon, 28 Jul 2008 19:13:50 +0200 Subject: Re: [PATCH 12/30] mm: memory reserve management From: Peter Zijlstra In-Reply-To: <1217263769.15724.32.camel@calx> References: <20080724140042.408642539@chello.nl> <20080724141530.127530749@chello.nl> <1217239564.7813.36.camel@penberg-laptop> <1217263769.15724.32.camel@calx> Content-Type: text/plain Date: Mon, 28 Jul 2008 19:13:43 +0200 Message-Id: <1217265223.18049.22.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Matt Mackall Cc: Pekka Enberg , Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, trond.myklebust@fys.uio.no, Daniel Lezcano , Neil Brown , cl@linux-foundation.org List-ID: On Mon, 2008-07-28 at 11:49 -0500, Matt Mackall wrote: > On Mon, 2008-07-28 at 13:06 +0300, Pekka Enberg wrote: > > We're trying to get rid of kfree() so I'd __kfree_reserve() could to > > mm/sl?b.c. Matt, thoughts? > > I think you mean ksize there. My big issue is that we need to make it > clear that ksize pairs -only- with kmalloc and that > ksize(kmem_cache_alloc(...)) is a categorical error. Preferably, we do > this by giving it a distinct name, like kmalloc_size(). We can stick an > underbar in front of it to suggest you ought not be using it too. Right, both make sense, so _kmalloc_size() has my vote. > > > + /* > > > + * ksize gives the full allocated size vs the requested size we > > used to > > > + * charge; however since we round up to the nearest power of two, > > this > > > + * should all work nicely. > > > + */ > > SLOB doesn't do this, of course. But does that matter? I think you want > to charge the actual allocation size to the reserve in all cases, no? > That probably means calling ksize() on both alloc and free. Like said, I still need to do all the SLOB reservation stuff. That includes coming up with upper bound fragmentation loss. For SL[UA]B I use roundup_power_of_two for kmalloc sizes. Thus with the above ksize(), if we did p=kmalloc(x), then we'd account roundup_power_of_two(x), and that should be equal to roundup_power_of_two(ksize(p)), as ksize will always be smaller or equal to the roundup. I'm guessing the power of two upper bound is good for SLOB too - although I haven't tried proving it wrong or tighetening it. Only the kmem_cache_* reservation stuff would need some extra attention with SLOB. -- 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