From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id B17EA6B003D for ; Tue, 21 Apr 2009 06:05:29 -0400 (EDT) Date: Tue, 21 Apr 2009 11:05:30 +0100 From: Mel Gorman Subject: Re: [PATCH 10/25] Calculate the alloc_flags for allocation only once Message-ID: <20090421100530.GN12713@csn.ul.ie> References: <1240266011-11140-1-git-send-email-mel@csn.ul.ie> <1240266011-11140-11-git-send-email-mel@csn.ul.ie> <20090421165022.F13F.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20090421165022.F13F.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Linux Memory Management List , Christoph Lameter , Nick Piggin , Linux Kernel Mailing List , Lin Ming , Zhang Yanmin , Peter Zijlstra , Pekka Enberg , Andrew Morton List-ID: On Tue, Apr 21, 2009 at 06:03:25PM +0900, KOSAKI Motohiro wrote: > > Factor out the mapping between GFP and alloc_flags only once. Once factored > > out, it only needs to be calculated once but some care must be taken. > > > > [neilb@suse.de says] > > As the test: > > > > - if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE))) > > - && !in_interrupt()) { > > - if (!(gfp_mask & __GFP_NOMEMALLOC)) { > > > > has been replaced with a slightly weaker one: > > > > + if (alloc_flags & ALLOC_NO_WATERMARKS) { > > > > we need to ensure we don't recurse when PF_MEMALLOC is set. > > It seems good idea. > > > +static inline int > > +gfp_to_alloc_flags(gfp_t gfp_mask) > > +{ > > + struct task_struct *p = current; > > + int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET; > > + const gfp_t wait = gfp_mask & __GFP_WAIT; > > + > > + /* > > + * The caller may dip into page reserves a bit more if the caller > > + * cannot run direct reclaim, or if the caller has realtime scheduling > > + * policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will > > + * set both ALLOC_HARDER (!wait) and ALLOC_HIGH (__GFP_HIGH). > > + */ > > + if (gfp_mask & __GFP_HIGH) > > + alloc_flags |= ALLOC_HIGH; > > + > > + if (!wait) { > > + alloc_flags |= ALLOC_HARDER; > > + /* > > + * Ignore cpuset if GFP_ATOMIC (!wait) rather than fail alloc. > > + * See also cpuset_zone_allowed() comment in kernel/cpuset.c. > > + */ > > + alloc_flags &= ~ALLOC_CPUSET; > > + } else if (unlikely(rt_task(p)) && !in_interrupt()) > > wait==1 and in_interrupt==1 is never occur. > I think in_interrupt check can be removed. > Looks like it. I removed it now. > > /* Atomic allocations - we can't balance anything */ > > if (!wait) > > goto nopage; > > > > + /* Avoid recursion of direct reclaim */ > > + if (p->flags & PF_MEMALLOC) > > + goto nopage; > > + > > Again. old code doesn't only check PF_MEMALLOC, but also check TIF_MEMDIE. > But a direct reclaim will have PF_MEMALLOC set and doesn't care about the value of TIF_MEMDIE with respect to recursion. There is still a check made for TIF_MEMDIE for setting ALLOC_NO_WATERMARKS in gfp_to_alloc_flags() so that flag is still being taken care of. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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