From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [PATCH 03/33] mm: slub: add knowledge of reserve pages Date: Wed, 31 Oct 2007 21:46:02 +1100 Message-ID: <200710312146.03351.nickpiggin@yahoo.com.au> References: <20071030160401.296770000@chello.nl> <200710311437.28630.nickpiggin@yahoo.com.au> <1193827358.27652.126.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, trond.myklebust@fys.uio.no To: Peter Zijlstra Return-path: Received: from smtp101.mail.mud.yahoo.com ([209.191.85.211]:36151 "HELO smtp101.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753024AbXJaL56 (ORCPT ); Wed, 31 Oct 2007 07:57:58 -0400 In-Reply-To: <1193827358.27652.126.camel@twins> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wednesday 31 October 2007 21:42, Peter Zijlstra wrote: > On Wed, 2007-10-31 at 14:37 +1100, Nick Piggin wrote: > > On Wednesday 31 October 2007 03:04, Peter Zijlstra wrote: > > > Restrict objects from reserve slabs (ALLOC_NO_WATERMARKS) to allocation > > > contexts that are entitled to it. > > > > > > Care is taken to only touch the SLUB slow path. > > > > > > This is done to ensure reserve pages don't leak out and get consumed. > > > > I think this is generally a good idea (to prevent slab allocators > > from stealing reserve). However I naively think the implementation > > is a bit overengineered and thus has a few holes. > > > > Humour me, what was the problem with failing the slab allocation > > (actually, not fail but just call into the page allocator to do > > correct waiting / reclaim) in the slowpath if the process fails the > > watermark checks? > > Ah, we actually need slabs below the watermarks. Right, I'd still allow those guys to allocate slabs. Provided they have the right allocation context, right? > Its just that once I > allocated those slabs using __GFP_MEMALLOC/PF_MEMALLOC I don't want > allocation contexts that do not have rights to those pages to walk off > with objects. And I'd prevent these ones from doing so. Without keeping track of "reserve" pages, which doesn't feel too clean.