From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964877AbcHaPR0 (ORCPT ); Wed, 31 Aug 2016 11:17:26 -0400 Received: from mga06.intel.com ([134.134.136.31]:63033 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933887AbcHaPRY (ORCPT ); Wed, 31 Aug 2016 11:17:24 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,262,1470726000"; d="scan'208";a="3182571" From: "Huang\, Ying" To: Mel Gorman Cc: "Huang\, Ying" , Andrew Morton , , , , , , , Hugh Dickins , Shaohua Li , Minchan Kim , Rik van Riel , Tejun Heo , Wu Fengguang Subject: Re: [PATCH -v2] mm: Don't use radix tree writeback tags for pages in swap cache References: <1472578089-5560-1-git-send-email-ying.huang@intel.com> <20160831091459.GY8119@techsingularity.net> Date: Wed, 31 Aug 2016 08:17:24 -0700 In-Reply-To: <20160831091459.GY8119@techsingularity.net> (Mel Gorman's message of "Wed, 31 Aug 2016 10:14:59 +0100") Message-ID: <87oa49m0hn.fsf@yhuang-mobile.sh.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mel Gorman writes: > On Tue, Aug 30, 2016 at 10:28:09AM -0700, Huang, Ying wrote: >> From: Huang Ying >> >> 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_swap.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_inactive_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_writeback.page_endio.pmem_rw_page >> > > I didn't see anything wrong with the patch but it's worth highlighting > that this hunk means we are now out of GFP bits. Sorry, I don't know whether I understand your words. It is something about, __GFP_BITS_SHIFT == 26 So remainning bits in mapping_flags is 6. And now the latest bit is used for the flag introduced in the patch? Best Regards, Huang, Ying >> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h >> index 66a1260..2f5a65dd 100644 >> --- a/include/linux/pagemap.h >> +++ b/include/linux/pagemap.h >> @@ -25,6 +25,8 @@ enum mapping_flags { >> AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */ >> AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */ >> AS_EXITING = __GFP_BITS_SHIFT + 4, /* final truncate in progress */ >> + /* writeback related tags are not used */ >> + AS_NO_WRITEBACK_TAGS = __GFP_BITS_SHIFT + 5, >> }; >> From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f69.google.com (mail-pa0-f69.google.com [209.85.220.69]) by kanga.kvack.org (Postfix) with ESMTP id 59CB26B025E for ; Wed, 31 Aug 2016 11:17:25 -0400 (EDT) Received: by mail-pa0-f69.google.com with SMTP id ez1so95084414pab.1 for ; Wed, 31 Aug 2016 08:17:25 -0700 (PDT) Received: from mga01.intel.com (mga01.intel.com. [192.55.52.88]) by mx.google.com with ESMTPS id u190si358993pfb.43.2016.08.31.08.17.24 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 31 Aug 2016 08:17:24 -0700 (PDT) From: "Huang\, Ying" Subject: Re: [PATCH -v2] mm: Don't use radix tree writeback tags for pages in swap cache References: <1472578089-5560-1-git-send-email-ying.huang@intel.com> <20160831091459.GY8119@techsingularity.net> Date: Wed, 31 Aug 2016 08:17:24 -0700 In-Reply-To: <20160831091459.GY8119@techsingularity.net> (Mel Gorman's message of "Wed, 31 Aug 2016 10:14:59 +0100") Message-ID: <87oa49m0hn.fsf@yhuang-mobile.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: "Huang, Ying" , Andrew Morton , 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 , Shaohua Li , Minchan Kim , Rik van Riel , Tejun Heo , Wu Fengguang Mel Gorman writes: > On Tue, Aug 30, 2016 at 10:28:09AM -0700, Huang, Ying wrote: >> From: Huang Ying >> >> 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 A+- 2% +28.1% 3212076 A+- 7% vm-scalability.throughput >> 1207402 A+- 7% +22.3% 1476578 A+- 6% vmstat.swap.so >> 10.86 A+- 12% -23.4% 8.31 A+- 16% perf-profile.cycles-pp._raw_spin_lock_irq.__add_to_swap_cache.add_to_swap_cache.add_to_swap.shrink_page_list >> 10.82 A+- 13% -33.1% 7.24 A+- 14% perf-profile.cycles-pp._raw_spin_lock_irqsave.__remove_mapping.shrink_page_list.shrink_inactive_list.shrink_zone_memcg >> 10.36 A+- 11% -100.0% 0.00 A+- -1% perf-profile.cycles-pp._raw_spin_lock_irqsave.__test_set_page_writeback.bdev_write_page.__swap_writepage.swap_writepage >> 10.52 A+- 12% -100.0% 0.00 A+- -1% perf-profile.cycles-pp._raw_spin_lock_irqsave.test_clear_page_writeback.end_page_writeback.page_endio.pmem_rw_page >> > > I didn't see anything wrong with the patch but it's worth highlighting > that this hunk means we are now out of GFP bits. Sorry, I don't know whether I understand your words. It is something about, __GFP_BITS_SHIFT == 26 So remainning bits in mapping_flags is 6. And now the latest bit is used for the flag introduced in the patch? Best Regards, Huang, Ying >> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h >> index 66a1260..2f5a65dd 100644 >> --- a/include/linux/pagemap.h >> +++ b/include/linux/pagemap.h >> @@ -25,6 +25,8 @@ enum mapping_flags { >> AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */ >> AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */ >> AS_EXITING = __GFP_BITS_SHIFT + 4, /* final truncate in progress */ >> + /* writeback related tags are not used */ >> + AS_NO_WRITEBACK_TAGS = __GFP_BITS_SHIFT + 5, >> }; >> -- 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