From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02F45C433F5 for ; Thu, 21 Apr 2022 07:49:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 85B5A6B0071; Thu, 21 Apr 2022 03:49:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7E4BC6B0073; Thu, 21 Apr 2022 03:49:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 65E726B0074; Thu, 21 Apr 2022 03:49:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.25]) by kanga.kvack.org (Postfix) with ESMTP id 513186B0071 for ; Thu, 21 Apr 2022 03:49:28 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 2A7DD81785 for ; Thu, 21 Apr 2022 07:49:28 +0000 (UTC) X-FDA: 79380111216.27.7F5DD31 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by imf28.hostedemail.com (Postfix) with ESMTP id E1B14C001C for ; Thu, 21 Apr 2022 07:49:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650527367; x=1682063367; h=message-id:subject:from:to:cc:date:in-reply-to: references:mime-version:content-transfer-encoding; bh=ETP06IA+RyjcwFgY+scj0+OYU3vSsMZK3PEoX7of2Qw=; b=NSXzUuB+5yHil9eS1sjat/doLjvHwZKR846n5NmRwgmkfLD7gCjmAxmy vurMG9sx4x0xs4HKWfHD62V76eDyrxbuktGZ7mQk8cQXOa/yam0XJEdcr TCsShNBhiZvTjwN/1mh6Z68AWhADm1foyBDHQyUJizQtHw/tJ+Oqnv2N0 UZmWvGcAc/EY5kMGNAcBP221iDketqr1A27FBBxhKWBdtKXzeFXruJwLb W16ZGQYU35MtQYBGgeVociKaEgM/5Lac+6xzU1nNuH+G8wsPn6ilOyflh FqVOJuFPDovcOtFBEZ1jP1dxWxXPIkqQJTUw42auPhFFLudC8tILY60vV Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10323"; a="289383370" X-IronPort-AV: E=Sophos;i="5.90,278,1643702400"; d="scan'208";a="289383370" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Apr 2022 00:49:25 -0700 X-IronPort-AV: E=Sophos;i="5.90,278,1643702400"; d="scan'208";a="577079489" Received: from hanyulon-mobl1.ccr.corp.intel.com ([10.254.214.143]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Apr 2022 00:49:23 -0700 Message-ID: Subject: Re: [PATCH] mm: swap: determine swap device by using page nid From: "ying.huang@intel.com" To: Aaron Lu , Yang Shi Cc: Michal Hocko , Andrew Morton , Linux MM , Linux Kernel Mailing List Date: Thu, 21 Apr 2022 15:49:21 +0800 In-Reply-To: References: <20220407020953.475626-1-shy828301@gmail.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.3-1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=NSXzUuB+; spf=none (imf28.hostedemail.com: domain of ying.huang@intel.com has no SPF policy when checking 192.55.52.88) smtp.mailfrom=ying.huang@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Stat-Signature: xy38emdanwf6a9t3ejnpp1n7takcsk6j X-Rspamd-Queue-Id: E1B14C001C X-Rspamd-Server: rspam04 X-Rspam-User: X-HE-Tag: 1650527364-395193 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 2022-04-20 at 16:33 +0800, Aaron Lu wrote: > On Thu, Apr 07, 2022 at 10:36:54AM -0700, Yang Shi wrote: > > On Thu, Apr 7, 2022 at 1:12 AM Aaron Lu wrote: > > > > > > On Wed, Apr 06, 2022 at 07:09:53PM -0700, Yang Shi wrote: > > > > The swap devices are linked to per node priority lists, the swap device > > > > closer to the node has higher priority on that node's priority list. > > > > This is supposed to improve I/O latency, particularly for some fast > > > > devices. But the current code gets nid by calling numa_node_id() which > > > > actually returns the nid that the reclaimer is running on instead of the > > > > nid that the page belongs to. > > > > > > > > > > Right. > > > > > > > Pass the page's nid dow to get_swap_pages() in order to pick up the > > > > right swap device. But it doesn't work for the swap slots cache which > > > > is per cpu. We could skip swap slots cache if the current node is not > > > > the page's node, but it may be overkilling. So keep using the current > > > > node's swap slots cache. The issue was found by visual code inspection > > > > so it is not sure how much improvement could be achieved due to lack of > > > > suitable testing device. But anyway the current code does violate the > > > > design. > > > > > > > > > > I intentionally used the reclaimer's nid because I think when swapping > > > out to a device, it is faster when the device is on the same node as > > > the cpu. > > > > OK, the offline discussion with Huang Ying showed the design was to > > have page's nid in order to achieve better I/O performance (more > > noticeable on faster devices) since the reclaimer may be running on a > > different node from the reclaimed page. > > > > > > > > Anyway, I think I can make a test case where the workload allocates all > > > its memory on the remote node and its workingset memory is larger then > > > the available memory so swap is triggered, then we can see which way > > > achieves better performance. Sounds reasonable to you? > > > > Yeah, definitely, thank you so much. I don't have a fast enough device > > by hand to show the difference right now. If you could get some data > > it would be perfect. > > > > Failed to find a test box that has two NVMe disks attached to different > nodes and since Shanghai is locked down right now, we couldn't install > another NVMe on the box so I figured it might be OK to test on a box that > has a single NVMe attached to node 0 like this: > > 1) restrict the test processes to run on node 0 and allocate on node 1; > 2) restrict the test processes to run on node 1 and allocate on node 0. > > In case 1), the reclaimer's node id is the same as the swap device's so > it's the same as current behaviour and in case 2), the page's node id is > the same as the swap device's so it's what your patch proposed. > > The test I used is vm-scalability/case-swap-w-rand: > https://git.kernel.org/pub/scm/linux/kernel/git/wfg/vm-scalability.git/tree/case-swap-w-seq > which spawns $nr_task processes and each will mmap $size and then > randomly write to that area. I set nr_task=32 and $size=4G, so a total > of 128G memory will be needed and I used memory.limit_in_bytes to > restrict the available memory to 64G, to make sure swap is triggered. > > The reason why cgroup is used is to avoid waking up the per-node kswapd > which can trigger swapping with reclaimer/page/swap device all having the > same node id. > > And I don't see a measuable difference from the result: > case1(using reclaimer's node id) vm-scalability.throughput: 10574 KB/s > case2(using page's node id) vm-scalability.throughput: 10567 KB/s > > My interpretation of the result is, when reclaiming a remote page, it > doesn't matter much which swap device to use if the swap device is a IO > device. > > Later Ying reminded me we have test box that has optane installed on > different nodes so I also tested there: Icelake 2 sockets server with 2 > optane installed on each node. I did the test there like this: > 1) restrict the test processes to run on node 0 and allocate on node 1 >    and only swapon pmem0, which is the optane backed swap device on node 0; > 2) restrict the test processes to run on node 0 and allocate on node 1 >    and only swapon pmem1, which is the optane backed swap device on node 1. > > So case 1) is current behaviour and case 2) is what your patch proposed. > > With the same test and the same nr_task/size, the result is: > case1(using reclaimer's node id) vm-scalability.throughput: 71033 KB/s > case2(using page's node id) vm-scalability.throughput: 58753 KB/s > The per-node swap device support is more about swap-in latency than swap-out throughput. I suspect the test case is more about swap-out throughput. perf profiling can show this. For swap-in latency, we can use pmbench, which can output latency information. Best Regards, Huang, Ying [snip]