From: Rik van Riel <riel@redhat.com>
To: "Huang, Ying" <ying.huang@intel.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: tim.c.chen@intel.com, dave.hansen@intel.com,
andi.kleen@intel.com, aaron.lu@intel.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Hugh Dickins <hughd@google.com>,
Shaohua Li <shli@kernel.org>, Minchan Kim <minchan@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
Tejun Heo <tj@kernel.org>, Wu Fengguang <fengguang.wu@intel.com>
Subject: Re: [PATCH -v2] mm: Don't use radix tree writeback tags for pages in swap cache
Date: Tue, 30 Aug 2016 14:29:52 -0400 [thread overview]
Message-ID: <1472581792.10218.52.camel@redhat.com> (raw)
In-Reply-To: <1472578089-5560-1-git-send-email-ying.huang@intel.com>
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On Tue, 2016-08-30 at 10:28 -0700, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
>
> File pages use a set of radix tree tags (DIRTY, TOWRITE, WRITEBACK,
> etc.) to accelerate finding the pages with a specific tag in the
> radix
> tree during inode writeback. But for anonymous pages in the swap
> cache, there is no inode writeback. So there is no need to find the
> pages with some writeback tags in the radix tree. It is not
> necessary
> to touch radix tree writeback tags for pages in the swap cache.
>
> Per Rik van Riel's suggestion, a new flag AS_NO_WRITEBACK_TAGS is
> introduced for address spaces which don't need to update the
> writeback
> tags. The flag is set for swap caches. It may be used for DAX file
> systems, etc.
>
> With this patch, the swap out bandwidth improved 22.3% (from ~1.2GB/s
> to
> ~ 1.48GBps) in the vm-scalability swap-w-seq test case with 8
> processes.
> The test is done on a Xeon E5 v3 system. The swap device used is a
> RAM
> simulated PMEM (persistent memory) device. The improvement comes
> from
> the reduced contention on the swap cache radix tree lock. To test
> sequential swapping out, the test case uses 8 processes, which
> sequentially allocate and write to the anonymous pages until RAM and
> part of the swap device is used up.
>
> Details of comparison is as follow,
>
> base base+patch
> ---------------- --------------------------
> %stddev %change %stddev
> \ | \
> 2506952 ± 2% +28.1% 3212076 ± 7% vm-
> scalability.throughput
> 1207402 ± 7% +22.3% 1476578 ± 6% vmstat.swap.so
> 10.86 ± 12% -23.4% 8.31 ± 16% perf-profile.cycles-
> pp._raw_spin_lock_irq.__add_to_swap_cache.add_to_swap_cache.add_to_sw
> ap.shrink_page_list
> 10.82 ± 13% -33.1% 7.24 ± 14% perf-profile.cycles-
> pp._raw_spin_lock_irqsave.__remove_mapping.shrink_page_list.shrink_in
> active_list.shrink_zone_memcg
> 10.36 ± 11% -100.0% 0.00 ± -1% perf-profile.cycles-
> pp._raw_spin_lock_irqsave.__test_set_page_writeback.bdev_write_page._
> _swap_writepage.swap_writepage
> 10.52 ± 12% -100.0% 0.00 ± -1% perf-profile.cycles-
> pp._raw_spin_lock_irqsave.test_clear_page_writeback.end_page_writebac
> k.page_endio.pmem_rw_page
>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Shaohua Li <shli@kernel.org>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Wu Fengguang <fengguang.wu@intel.com>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>
Acked-by: Rik van Riel <riel@redhat.com>
--
All rights reversed
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next prev parent reply other threads:[~2016-08-30 18:30 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-30 17:28 [PATCH -v2] mm: Don't use radix tree writeback tags for pages in swap cache Huang, Ying
2016-08-30 18:29 ` Rik van Riel [this message]
2016-08-31 9:14 ` Mel Gorman
2016-08-31 15:17 ` Huang, Ying
2016-08-31 15:39 ` Mel Gorman
2016-08-31 15:44 ` Huang, Ying
2016-08-31 21:35 ` Andi Kleen
2016-08-31 21:30 ` Andrew Morton
2016-09-01 8:51 ` Mel Gorman
2016-09-01 9:13 ` Michal Hocko
2016-09-12 11:16 ` [PATCH 0/2] do not squash mapping flags and gfp_mask together (was: Re: [PATCH -v2] mm: Don't use radix tree writeback tags for pages in) Michal Hocko
2016-09-12 11:16 ` [PATCH 1/2] fs: use mapping_set_error instead of opencoded set_bit Michal Hocko
2016-09-12 22:11 ` Andrew Morton
2016-09-12 22:18 ` Andrew Morton
2016-09-13 6:53 ` Michal Hocko
2016-09-13 21:29 ` Andrew Morton
2016-09-12 11:16 ` [PATCH 2/2] mm: split gfp_mask and mapping flags into separate fields Michal Hocko
2016-09-12 11:48 ` Michal Hocko
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