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imf22.hostedemail.com; dkim=none; spf=pass (imf22.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1709540496; a=rsa-sha256; cv=none; b=IgOcJqJ1gGyptz9AkfiWMdT3doA//XLuxDdgVxx3y20z92eecNDNhYYQhsbGp6dnEV6KS5 c5KX9OQIFFpPmc4fsXd0MBEojlwtl2kX913mVjAp0vfBlYTIklh+ur/eawIPNumzcnKXWr owPh9gyyR2YOzFKQJew85lk8HErY9vY= X-AuditID: a67dfc5b-d6dff70000001748-70-65e58488cc98 From: Byungchul Park To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, yuzhao@google.com, ying.huang@intel.com, hannes@cmpxchg.org Subject: [PATCH v6] mm, vmscan: retry kswapd's priority loop with cache_trim_mode off on failure Date: Mon, 4 Mar 2024 17:21:18 +0900 Message-Id: <20240304082118.20499-1-byungchul@sk.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20240304033611.GD13332@system.software.com> References: <20240304033611.GD13332@system.software.com> X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFupjluLIzCtJLcpLzFFi42LhesuzULej5WmqQfdxLYs569ewWaze5Gtx edccNot7a/6zWpycNZnF4t2EL6wObB6H37xn9liwqdRj8Z6XTB6bPk1i9zgx4zeLx+dNcgFs UVw2Kak5mWWpRfp2CVwZX0/0sRWsM6643LmSvYHxlmoXIyeHhICJxI1/k5hg7MWTTrKD2GwC 6hI3bvxkBrFFBGQlpv49z9LFyMXBLDCFUWLFvXY2kISwQILE79VrWEFsFgFVibfH+8HivAKm EpNmXGCEGCovsXrDAaBBHBycApYSP7rcQMJCAhYS9+a1sILMlBD4yipx8MZjFoh6SYmDK26w TGDkXcDIsIpRKDOvLDcxM8dEL6MyL7NCLzk/dxMjMJSW1f6J3sH46ULwIUYBDkYlHt6Mziep QqyJZcWVuYcYJTiYlUR4a34BhXhTEiurUovy44tKc1KLDzFKc7AoifMafStPERJITyxJzU5N LUgtgskycXBKNTD6C69bF2XrMXHHnNzulEKdFAvbL/klkt/WfVt7V+ViZWDOwRfpa5tsmxdO qyzR2czZ1GzC0MC+eEO9B2fgXeuzLlJfehj6r954uOnVio31Zjd8YtRlo89uYBdY0rXHxvLS cZ9pijF3Y2/++ud1oYF54e3zNQtZ9y8MeeOvPGWlxPnlL1Y+39ShxFKckWioxVxUnAgAkZ2W UyECAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrKJMWRmVeSWpSXmKPExsXC5WfdrNvR8jTVoOesnMWc9WvYLFZv8rU4 PPckq8XlXXPYLO6t+c9qcXLWZBaLdxO+sDqwexx+857ZY8GmUo/Fe14yeWz6NInd48SM3ywe i198YPL4vEkugD2KyyYlNSezLLVI3y6BK+PriT62gnXGFZc7V7I3MN5S7WLk5JAQMJFYPOkk O4jNJqAucePGT2YQW0RAVmLq3/MsXYxcHMwCUxglVtxrZwNJCAskSPxevYYVxGYRUJV4e7wf LM4rYCoxacYFRoih8hKrNxwAGsTBwSlgKfGjyw0kLCRgIXFvXgvrBEauBYwMqxhFMvPKchMz c0z1irMzKvMyK/SS83M3MQIDY1ntn4k7GL9cdj/EKMDBqMTDO2HNk1Qh1sSy4srcQ4wSHMxK Irw1v4BCvCmJlVWpRfnxRaU5qcWHGKU5WJTEeb3CUxOEBNITS1KzU1MLUotgskwcnFINjPX7 6ytzmLLLHqhU9PB+vvt/1pRNb9OXXNm4lnv91ml7XrxcvXBT0IQbzl1yjIkm21a4Raxu4So9 qPJ7gu75KNnMN5eW1PAf7j/4v1OsUN/BmkfvS6zp1l/is5af18yV8vRtfWx4Szl35euWV5It 2Z4r0xN0/smcZJBV5JQ5mN41XyZ+//k6biWW4oxEQy3mouJEAMHkLOcIAgAA X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 34AE0C000C X-Rspam-User: X-Stat-Signature: e5rcgco97am65ssaumi5eipduz4nt9p7 X-Rspamd-Server: rspam01 X-HE-Tag: 1709540493-213220 X-HE-Meta: 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 lmwCMWO2 RswbDqnkOtGIuYIBOPbJgCVkiJ9Xkaiy7xIJnc6eSMO46s6/EcLE17iFPVLftnRAzvpMp6cpdluZY71U= 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: List-Subscribe: List-Unsubscribe: Changes from v5: 1. Make it retry the kswapd's scan priority loop with cache_trim_mode off *only if* the mode didn't work in the previous loop. (feedbacked by Huang Ying) 2. Take into account 'break's from the priority loop when making the decision whether to retry. (feedbacked by Huang Ying) 3. Update the test result in the commit message. Changes from v4: 1. Make other scans start with may_cache_trim_mode = 1. Changes from v3: 1. Update the test result in the commit message with v4. 2. Retry the whole priority loop with cache_trim_mode off again, rather than forcing the mode off at the highest priority, when the mode doesn't work. (feedbacked by Johannes Weiner) Changes from v2: 1. Change the condition to stop cache_trim_mode. From - Stop it if it's at high scan priorities, 0 or 1. To - Stop it if it's at high scan priorities, 0 or 1, and the mode didn't work in the previous turn. (feedbacked by Huang Ying) 2. Change the test result in the commit message after testing with the new logic. Changes from v1: 1. Add a comment describing why this change is necessary in code and rewrite the commit message with how to reproduce and what the result is using vmstat. (feedbacked by Andrew Morton and Yu Zhao) 2. Change the condition to avoid cache_trim_mode from 'sc->priority != 1' to 'sc->priority > 1' to reflect cases where the priority goes to zero all the way. (feedbacked by Yu Zhao) --->8--- From f811ee583158fd53d0e94d32ce5948fac4b17cfe Mon Sep 17 00:00:00 2001 From: Byungchul Park Date: Mon, 4 Mar 2024 15:27:37 +0900 Subject: [PATCH v6] mm, vmscan: retry kswapd's priority loop with cache_trim_mode off on failure With cache_trim_mode on, reclaim logic doesn't bother reclaiming anon pages. However, it should be more careful to use the mode because it's going to prevent anon pages from being reclaimed even if there are a huge number of anon pages that are cold and should be reclaimed. Even worse, that leads kswapd_failures to reach MAX_RECLAIM_RETRIES and stopping kswapd from functioning until direct reclaim eventually works to resume kswapd. So kswapd needs to retry its scan priority loop with cache_trim_mode off again if the mode doesn't work for reclaim. The problematic behavior can be reproduced by: CONFIG_NUMA_BALANCING enabled sysctl_numa_balancing_mode set to NUMA_BALANCING_MEMORY_TIERING numa node0 (8GB local memory, 16 CPUs) numa node1 (8GB slow tier memory, no CPUs) Sequence: 1) echo 3 > /proc/sys/vm/drop_caches 2) To emulate the system with full of cold memory in local DRAM, run the following dummy program and never touch the region: mmap(0, 8 * 1024 * 1024 * 1024, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_POPULATE, -1, 0); 3) Run any memory intensive work e.g. XSBench. 4) Check if numa balancing is working e.i. promotion/demotion. 5) Iterate 1) ~ 4) until numa balancing stops. With this, you could see that promotion/demotion are not working because kswapd has stopped due to ->kswapd_failures >= MAX_RECLAIM_RETRIES. Interesting vmstat delta's differences between before and after are like: +-----------------------+-------------------------------+ | interesting vmstat | before | after | +-----------------------+-------------------------------+ | nr_inactive_anon | 321935 | 1664772 | | nr_active_anon | 1780700 | 437834 | | nr_inactive_file | 30425 | 40882 | | nr_active_file | 14961 | 3012 | | pgpromote_success | 356 | 1293122 | | pgpromote_candidate | 21953245 | 1824148 | | pgactivate | 1844523 | 3311907 | | pgdeactivate | 50634 | 1554069 | | pgfault | 31100294 | 6518806 | | pgdemote_kswapd | 30856 | 2230821 | | pgscan_kswapd | 1861981 | 7667629 | | pgscan_anon | 1822930 | 7610583 | | pgscan_file | 39051 | 57046 | | pgsteal_anon | 386 | 2192033 | | pgsteal_file | 30470 | 38788 | | pageoutrun | 30 | 412 | | numa_hint_faults | 27418279 | 2875955 | | numa_pages_migrated | 356 | 1293122 | +-----------------------+-------------------------------+ Signed-off-by: Byungchul Park --- mm/vmscan.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index bba207f41b14..6fe45eca7766 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -108,6 +108,12 @@ struct scan_control { /* Can folios be swapped as part of reclaim? */ unsigned int may_swap:1; + /* Not allow cache_trim_mode to be turned on as part of reclaim? */ + unsigned int no_cache_trim_mode:1; + + /* Has cache_trim_mode failed at least once? */ + unsigned int cache_trim_mode_failed:1; + /* Proactive reclaim invoked by userspace through memory.reclaim */ unsigned int proactive:1; @@ -2268,7 +2274,8 @@ static void prepare_scan_control(pg_data_t *pgdat, struct scan_control *sc) * anonymous pages. */ file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE); - if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE)) + if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE) && + !sc->no_cache_trim_mode) sc->cache_trim_mode = 1; else sc->cache_trim_mode = 0; @@ -5967,6 +5974,8 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) */ if (reclaimable) pgdat->kswapd_failures = 0; + else if (sc->cache_trim_mode) + sc->cache_trim_mode_failed = 1; } /* @@ -6898,6 +6907,16 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx) sc.priority--; } while (sc.priority >= 1); + /* + * Restart only if it went through the priority loop all the way, + * but cache_trim_mode didn't work. + */ + if (!sc.nr_reclaimed && sc.priority < 1 && + !sc.no_cache_trim_mode && sc.cache_trim_mode_failed) { + sc.no_cache_trim_mode = 1; + goto restart; + } + if (!sc.nr_reclaimed) pgdat->kswapd_failures++;