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 B80CEC433F5 for ; Mon, 14 Mar 2022 23:38:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1A4E86B0071; Mon, 14 Mar 2022 19:38:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 158FF6B0072; Mon, 14 Mar 2022 19:38:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EE8648D0001; Mon, 14 Mar 2022 19:38:41 -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 DED596B0071 for ; Mon, 14 Mar 2022 19:38:41 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id 9E39A60C6B for ; Mon, 14 Mar 2022 23:38:41 +0000 (UTC) X-FDA: 79244608842.03.4479719 Received: from mail-pj1-f44.google.com (mail-pj1-f44.google.com [209.85.216.44]) by imf22.hostedemail.com (Postfix) with ESMTP id 1AFA6C000A for ; Mon, 14 Mar 2022 23:38:40 +0000 (UTC) Received: by mail-pj1-f44.google.com with SMTP id rm8-20020a17090b3ec800b001c55791fdb1so863569pjb.1 for ; Mon, 14 Mar 2022 16:38:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=N4obkUD8+Xm15wKaQvsDfW38K//v1SvAKl3Zz6bdAF8=; b=CX0UxRl7yteSgeLkynLXlv/zDjZEe0djx5kWxYBmDLeLdB6pkgl/LH3Rqp+2e7E+ZB oDrEhVr82GizbOvFz6pRQl5HczpIMDAxcCZJsLjAowxkvvAteGe50tTBuZuj7fGmgNyW Q6jyc5nRJkTCkHHUgYobnEtL85JD8gKf2jjLXzAT+3feDX4QxgKRN9NdpqRa+0v4xfLj cWMWDw4M8JyI26GYVxHF14mzq/i2nWjorpSCOfqY+ViN2lFH1073nNxifCCW83lurE4g pMP/VSb5E0Qy5yymmk4J6Q0RHZ3RzC4UQX1cPKpB4zBl7uEv/rghiBCVaTVPEE4Sxsun ZN2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=N4obkUD8+Xm15wKaQvsDfW38K//v1SvAKl3Zz6bdAF8=; b=Fqe3aPEUUePb09mEB/S6m5CrkEX4LmnJNhRrP7hMTc3q35/Uwjcmx6LG8fdroVC3zW 8sYwkzZ0XRXlooPJyM1MAXYQ2KXwz/dOKJOKCRdt2+B9w1m4cqg2fjY2Qolv8CCxd4ju K79CwMD77feSYPHAMDZ9ppnHBEyG1YDhob5XaVLDoxoFMg5V434W51NsApYJGMrKK/3y XufjrFYKjsOr1pmgiSpORSkGpHKzRaKG01h8wbPXK30oesTuNrf8h9uFzPRWRx9jNsrB dp8UxrWdGtmiPPC2NqrIg9QeY3twH9jASbNSA1c0q73aKQrTh0fteXBxLyGJPZVSYf/v aaWw== X-Gm-Message-State: AOAM532HvnrxMBK4cPXGqjNOko00QywuZ3Vb6Hs5FYbP76rQnrXoJW6J QcCOEz5d2TKHv3CP82AdSfk= X-Google-Smtp-Source: ABdhPJw8yRb7sdUwWB/JBXh4wMyTG4fG1xh0oPeDmrnBqnraMyyeVBHrVOHl/tNSRyifDNvg/Pj6Cw== X-Received: by 2002:a17:902:dacc:b0:152:268:27d9 with SMTP id q12-20020a170902dacc00b00152026827d9mr25586273plx.76.1647301119933; Mon, 14 Mar 2022 16:38:39 -0700 (PDT) Received: from barry-desktop.hub ([2407:7000:8942:5500:8d71:31d1:e9fc:88f3]) by smtp.gmail.com with ESMTPSA id b10-20020a056a00114a00b004f784ba5e6asm15128066pfm.17.2022.03.14.16.38.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Mar 2022 16:38:39 -0700 (PDT) From: Barry Song <21cnbao@gmail.com> To: yuzhao@google.com Cc: 21cnbao@gmail.com, Hi-Angel@yandex.ru, Michael@michaellarabel.com, ak@linux.intel.com, akpm@linux-foundation.org, aneesh.kumar@linux.ibm.com, axboe@kernel.dk, bgeffon@google.com, catalin.marinas@arm.com, corbet@lwn.net, d@chaos-reins.com, dave.hansen@linux.intel.com, djbyrne@mtu.edu, hannes@cmpxchg.org, hdanton@sina.com, heftig@archlinux.org, holger@applied-asynchrony.com, jsbarnes@google.com, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mgorman@suse.de, mhocko@kernel.org, oleksandr@natalenko.name, page-reclaim@google.com, riel@surriel.com, rppt@kernel.org, sofia.trinh@edi.works, steven@liquorix.net, suleiman@google.com, szhai2@cs.rochester.edu, torvalds@linux-foundation.org, vbabka@suse.cz, will@kernel.org, willy@infradead.org, x86@kernel.org, ying.huang@intel.com Subject: Re: [PATCH v7 04/12] mm: multigenerational LRU: groundwork Date: Tue, 15 Mar 2022 12:38:12 +1300 Message-Id: <20220314233812.9011-1-21cnbao@gmail.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 1AFA6C000A X-Stat-Signature: 4johxepqexp8yg9oijqdbn6rkr9oyhh6 X-Rspam-User: Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=CX0UxRl7; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf22.hostedemail.com: domain of 21cnbao@gmail.com designates 209.85.216.44 as permitted sender) smtp.mailfrom=21cnbao@gmail.com X-Rspamd-Server: rspam02 X-HE-Tag: 1647301120-431464 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 Tue, Mar 15, 2022 at 5:45 AM Yu Zhao wrote: > > On Mon, Mar 14, 2022 at 5:12 AM Barry Song <21cnbao@gmail.com> wrote: > > > > > > > > > > > > > > > We used to put a faulted file page in inactive, if we access it a > > > > > > > second time, it can be promoted > > > > > > > to active. then in recent years, we have also applied this to anon > > > > > > > pages while kernel adds > > > > > > > workingset protection for anon pages. so basically both anon and file > > > > > > > pages go into the inactive > > > > > > > list for the 1st time, if we access it for the second time, they go to > > > > > > > the active list. if we don't access > > > > > > > it any more, they are likely to be reclaimed as they are inactive. > > > > > > > we do have some special fastpath for code section, executable file > > > > > > > pages are kept on active list > > > > > > > as long as they are accessed. > > > > > > > > > > > > Yes. > > > > > > > > > > > > > so all of the above concerns are actually not that correct? > > > > > > > > > > > > They are valid concerns but I don't know any popular workloads that > > > > > > care about them. > > > > > > > > > > Hi Yu, > > > > > here we can get a workload in Kim's patchset while he added workingset > > > > > protection > > > > > for anon pages: > > > > > https://patchwork.kernel.org/project/linux-mm/cover/1581401993-20041-1-git-send-email-iamjoonsoo.kim@lge.com/ > > > > > > > > Thanks. I wouldn't call that a workload because it's not a real > > > > application. By popular workloads, I mean applications that the > > > > majority of people actually run on phones, in cloud, etc. > > > > > > > > > anon pages used to go to active rather than inactive, but kim's patchset > > > > > moved to use inactive first. then only after the anon page is accessed > > > > > second time, it can move to active. > > > > > > > > Yes. To clarify, the A-bit doesn't really mean the first or second > > > > access. It can be many accesses each time it's set. > > > > > > > > > "In current implementation, newly created or swap-in anonymous page is > > > > > > > > > > started on the active list. Growing the active list results in rebalancing > > > > > active/inactive list so old pages on the active list are demoted to the > > > > > inactive list. Hence, hot page on the active list isn't protected at all. > > > > > > > > > > Following is an example of this situation. > > > > > > > > > > Assume that 50 hot pages on active list and system can contain total > > > > > 100 pages. Numbers denote the number of pages on active/inactive > > > > > list (active | inactive). (h) stands for hot pages and (uo) stands for > > > > > used-once pages. > > > > > > > > > > 1. 50 hot pages on active list > > > > > 50(h) | 0 > > > > > > > > > > 2. workload: 50 newly created (used-once) pages > > > > > 50(uo) | 50(h) > > > > > > > > > > 3. workload: another 50 newly created (used-once) pages > > > > > 50(uo) | 50(uo), swap-out 50(h) > > > > > > > > > > As we can see, hot pages are swapped-out and it would cause swap-in later." > > > > > > > > > > Is MGLRU able to avoid the swap-out of the 50 hot pages? > > > > > > > > I think the real question is why the 50 hot pages can be moved to the > > > > inactive list. If they are really hot, the A-bit should protect them. > > > > > > This is a good question. > > > > > > I guess it  is probably because the current lru is trying to maintain a balance > > > between the sizes of active and inactive lists. Thus, it can shrink active list > > > even though pages might be still "hot" but not the recently accessed ones. > > > > > > 1. 50 hot pages on active list > > > 50(h) | 0 > > > > > > 2. workload: 50 newly created (used-once) pages > > > 50(uo) | 50(h) > > > > > > 3. workload: another 50 newly created (used-once) pages > > > 50(uo) | 50(uo), swap-out 50(h) > > > > > > the old kernel without anon workingset protection put workload 2 on active, so > > > pushed 50 hot pages from active to inactive. workload 3 would further contribute > > > to evict the 50 hot pages. > > > > > > it seems mglru doesn't demote pages from the youngest generation to older > > > generation only in order to balance the list size? so mglru is probably safe > > > in these cases. > > > > > > I will run some tests mentioned in Kim's patchset and report the result to you > > > afterwards. > > > > > > > Hi Yu, > > I did find putting faulted pages to the youngest generation lead to some > > regression in the case ebizzy Kim's patchset mentioned while he tried > > to support workingset protection for anon pages. > > i did a little bit modification for rand_chunk() which is probably similar > > with the modifcation() Kim mentioned in his patchset. The modification > > can be found here: > > https://github.com/21cnbao/ltp/commit/7134413d747bfa9ef > > > > The test env is a x86 machine in which I have set memory size to 2.5GB and > > set zRAM to 2GB and disabled external disk swap. > > > > with the vanilla kernel: > > \time -v ./a.out -vv -t 4 -s 209715200 -S 200000 > > > > so we have 10 chunks and 4 threads, each trunk is 209715200(200MB) > > > > typical result: > >         Command being timed: "./a.out -vv -t 4 -s 209715200 -S 200000" > >         User time (seconds): 36.19 > >         System time (seconds): 229.72 > >         Percent of CPU this job got: 371% > >         Elapsed (wall clock) time (h:mm:ss or m:ss): 1:11.59 > >         Average shared text size (kbytes): 0 > >         Average unshared data size (kbytes): 0 > >         Average stack size (kbytes): 0 > >         Average total size (kbytes): 0 > >         Maximum resident set size (kbytes): 2166196 > >         Average resident set size (kbytes): 0 > >         Major (requiring I/O) page faults: 9990128 > >         Minor (reclaiming a frame) page faults: 33315945 > >         Voluntary context switches: 59144 > >         Involuntary context switches: 167754 > >         Swaps: 0 > >         File system inputs: 2760 > >         File system outputs: 8 > >         Socket messages sent: 0 > >         Socket messages received: 0 > >         Signals delivered: 0 > >         Page size (bytes): 4096 > >         Exit status: 0 > > > > with gen_lru and lru_gen/enabled=0x3: > > typical result: > > Command being timed: "./a.out -vv -t 4 -s 209715200 -S 200000" > > User time (seconds): 36.34 > > System time (seconds): 276.07 > > Percent of CPU this job got: 378% > > Elapsed (wall clock) time (h:mm:ss or m:ss): 1:22.46 > >            **** 15% time + > > Average shared text size (kbytes): 0 > > Average unshared data size (kbytes): 0 > > Average stack size (kbytes): 0 > > Average total size (kbytes): 0 > > Maximum resident set size (kbytes): 2168120 > > Average resident set size (kbytes): 0 > > Major (requiring I/O) page faults: 13362810 > >              ***** 30% page fault + > > Minor (reclaiming a frame) page faults: 33394617 > > Voluntary context switches: 55216 > > Involuntary context switches: 137220 > > Swaps: 0 > > File system inputs: 4088 > > File system outputs: 8 > > Socket messages sent: 0 > > Socket messages received: 0 > > Signals delivered: 0 > > Page size (bytes): 4096 > > Exit status: 0 > > > > with gen_lru and lru_gen/enabled=0x7: > > typical result: > > Command being timed: "./a.out -vv -t 4 -s 209715200 -S 200000" > > User time (seconds): 36.13 > > System time (seconds): 251.71 > > Percent of CPU this job got: 378% > > Elapsed (wall clock) time (h:mm:ss or m:ss): 1:16.00 > >          *****better than enabled=0x3, worse than vanilla > > Average shared text size (kbytes): 0 > > Average unshared data size (kbytes): 0 > > Average stack size (kbytes): 0 > > Average total size (kbytes): 0 > > Maximum resident set size (kbytes): 2120988 > > Average resident set size (kbytes): 0 > > Major (requiring I/O) page faults: 12706512 > > Minor (reclaiming a frame) page faults: 33422243 > > Voluntary context switches: 49485 > > Involuntary context switches: 126765 > > Swaps: 0 > > File system inputs: 2976 > > File system outputs: 8 > > Socket messages sent: 0 > > Socket messages received: 0 > > Signals delivered: 0 > > Page size (bytes): 4096 > > Exit status: 0 > > > > I can also reproduce the problem on arm64. > > > > I am not saying this is going to block mglru from being mainlined. But  I am > > still curious if this is an issue worth being addressed somehow in mglru. > > You've missed something very important: *thoughput* :) > noop :-) in the test case, there are 4 threads. they are searching a key in 10 chunks of memory. for each chunk, the size is 200MB. a "random" chunk index is returned for those threads to search. but chunk2 is the hottest, and chunk3, 7, 4 are relatively hotter than others. static inline unsigned int rand_chunk(void) { /* simulate hot and cold chunk */ unsigned int rand[16] = {2, 2, 3, 4, 5, 2, 6, 7, 9, 2, 8, 3, 7, 2, 2, 4}; static int nr = 0; return rand[nr++%16]; } each thread does search_mem(): static unsigned int search_mem(void) { record_t key, *found; record_t *src, *copy; unsigned int chunk; size_t copy_size = chunk_size; unsigned int i; unsigned int state = 0; /* run 160 loops or till timeout */ for (i = 0; threads_go == 1 && i < 160; i++) { chunk = rand_chunk(); src = mem[chunk]; ... copy = alloc_mem(copy_size); ... memcpy(copy, src, copy_size); key = rand_num(copy_size / record_size, &state); bsearch(&key, copy, copy_size / record_size, record_size, compare); /* Below check is mainly for memory corruption or other bug */ if (found == NULL) { fprintf(stderr, "Couldn't find key %zd\n", key); exit(1); } } /* end if ! touch_pages */ free_mem(copy, copy_size); } return (i); } each thread picks up a chunk, then allocates a new memory and copies the chunk to the new allocated memory, and searches a key in the allocated memory. as i have set time to rather big by -S, so each thread actually exits while it completes 160 loops. $ \time -v ./ebizzy -t 4 -s $((200*1024*1024)) -S 6000000 so the one who finishes the whole jobs earlier wins in throughput as well. > Dollars to doughnuts there was a large increase in throughput -- I > haven't tried this benchmark but I've seen many reports similar to > this one. I have no doubt about this. I am just trying to figure out some potential we can further achieve in mglru. Thanks, Barry