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 <[email protected]> > Acked-by: David S. Miller <[email protected]> > Cc: Neil Brown <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Mike Christie <[email protected]> > Cc: Eric B Munson <[email protected]> > Cc: Eric Dumazet <[email protected]> > Cc: Sebastian Andrzej Siewior <[email protected]> > Cc: Mel Gorman <[email protected]> > Cc: Christoph Lameter <[email protected]> > Signed-off-by: Andrew Morton <[email protected]> > Signed-off-by: Linus Torvalds <[email protected]> >
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 <[email protected]> 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 <[email protected]> --- 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 ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
