Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755913Ab2HTJKl (ORCPT ); Mon, 20 Aug 2012 05:10:41 -0400 Received: from cantor2.suse.de ([195.135.220.15]:52508 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753721Ab2HTJKj (ORCPT ); Mon, 20 Aug 2012 05:10:39 -0400 Date: Mon, 20 Aug 2012 10:04:44 +0100 From: Mel Gorman To: Sage Weil Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, ceph-devel@vger.kernel.org, neilb@suse.de, a.p.zijlstra@chello.nl, michaelc@cs.wisc.edu, emunson@mgebm.net, eric.dumazet@gmail.com, sebastian@breakpoint.cc, cl@linux.com, akpm@linux-foundation.org, torvalds@linux-foundation.org Subject: Re: regression with poll(2) Message-ID: <20120820090443.GA3275@suse.de> References: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4403 Lines: 127 On Sun, Aug 19, 2012 at 11:49:31AM -0700, Sage Weil wrote: > I've bisected and identified this commit: > > netvm: propagate page->pfmemalloc to skb > > The skb->pfmemalloc flag gets set to true iff during the slab allocation > of data in __alloc_skb that the the PFMEMALLOC reserves were used. If the > packet is fragmented, it is possible that pages will be allocated from the > PFMEMALLOC reserve without propagating this information to the skb. This > patch propagates page->pfmemalloc from pages allocated for fragments to > the skb. > > Signed-off-by: Mel Gorman > Acked-by: David S. Miller > Cc: Neil Brown > Cc: Peter Zijlstra > Cc: Mike Christie > Cc: Eric B Munson > Cc: Eric Dumazet > Cc: Sebastian Andrzej Siewior > Cc: Mel Gorman > Cc: Christoph Lameter > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds > Ok, thanks. > I've retested several times and confirmed that this change leads to the > breakage, and also confirmed that reverting it on top of -rc1 also fixes > the problem. > > I've also added some additional instrumentation to my code and confirmed > that the process is blocking on poll(2) while netstat is reporting > data available on the socket. > > What can I do to help track this down? > Can the following patch be tested please? It is reported to fix an fio regression that may be similar to what you are experiencing but has not been picked up yet. ---8<--- From: Alex Shi Subject: [PATCH] mm: correct page->pfmemalloc to fix deactivate_slab regression commit cfd19c5a9ec (mm: only set page->pfmemalloc when ALLOC_NO_WATERMARKS was used) try to narrow down page->pfmemalloc setting, but it missed some places the pfmemalloc should be set. So, in __slab_alloc, the unalignment pfmemalloc and ALLOC_NO_WATERMARKS cause incorrect deactivate_slab() on our core2 server: 64.73% fio [kernel.kallsyms] [k] _raw_spin_lock | --- _raw_spin_lock | |---0.34%-- deactivate_slab | __slab_alloc | kmem_cache_alloc | | That causes our fio sync write performance has 40% regression. This patch move the checking in get_page_from_freelist, that resolved this issue. Signed-off-by: Alex Shi --- mm/page_alloc.c | 21 +++++++++++---------- 1 files changed, 11 insertions(+), 10 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 009ac28..07f1924 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1928,6 +1928,17 @@ this_zone_full: zlc_active = 0; goto zonelist_scan; } + + if (page) + /* + * page->pfmemalloc is set when ALLOC_NO_WATERMARKS was + * necessary to allocate the page. The expectation is + * that the caller is taking steps that will free more + * memory. The caller should avoid the page being used + * for !PFMEMALLOC purposes. + */ + page->pfmemalloc = !!(alloc_flags & ALLOC_NO_WATERMARKS); + return page; } @@ -2389,14 +2400,6 @@ rebalance: zonelist, high_zoneidx, nodemask, preferred_zone, migratetype); if (page) { - /* - * page->pfmemalloc is set when ALLOC_NO_WATERMARKS was - * necessary to allocate the page. The expectation is - * that the caller is taking steps that will free more - * memory. The caller should avoid the page being used - * for !PFMEMALLOC purposes. - */ - page->pfmemalloc = true; goto got_pg; } } @@ -2569,8 +2572,6 @@ retry_cpuset: page = __alloc_pages_slowpath(gfp_mask, order, zonelist, high_zoneidx, nodemask, preferred_zone, migratetype); - else - page->pfmemalloc = false; trace_mm_page_alloc(page, order, gfp_mask, migratetype); -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/