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imf20.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf20.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1708680895; a=rsa-sha256; cv=none; b=Kx8AY6YYnVt3J7RDnwwEtbLvSl7/P757dw8ZyjKAzF2JbKRI5yAAJa7kgqc8lmTcElr2/K VvKTXVRUPinCVTqkX89lXB2aB+NfwEsNVrxFif9fh5hNnVJBNc/QrQuW4brT0h7vwmfCZl w7SMdEs/aT/EzelRapsumiLkekYfSJg= X-AuditID: a67dfc5b-d6dff70000001748-de-65d866b65faa Date: Fri, 23 Feb 2024 18:34:41 +0900 From: Byungchul Park To: "Huang, Ying" Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, yuzhao@google.com Subject: Re: [PATCH v3] mm, vmscan: do not turn on cache_trim_mode if it doesn't work Message-ID: <20240223093441.GA1612@system.software.com> References: <20240223054407.14829-1-byungchul@sk.com> <87o7c7h6ql.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87o7c7h6ql.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrJLMWRmVeSWpSXmKPExsXC9ZZnke62tBupBrtmGVjMWb+GzeLyrjls FvfW/Ge1ODlrMovFuwlfWB1YPRZsKvVYvOclk8emT5PYPU7M+M3i8XmTXABrFJdNSmpOZllq kb5dAlfGjTfXWQqeWlf8XjmHsYHxjE4XIyeHhICJxNxp19i7GDnA7I2vpUFMFgFViRVn4kEq 2ATUJW7c+MkMYosIaEh8WricHcRmFqiVeHxnJhuILSwQLtExdzcriM0rYC6xt3kFWI2QQKZE y8XdzBBxQYmTM5+wQPRqSdz495IJZBWzgLTE8n8cIGFOATuJX9NvMoLYogLKEge2HQcq4QI6 bA6bxO+FD9ghLpaUOLjiBssERoFZSMbOQjJ2FsLYBYzMqxiFMvPKchMzc0z0MirzMiv0kvNz NzECA3hZ7Z/oHYyfLgQfYhTgYFTi4S1IvJ4qxJpYVlyZe4hRgoNZSYSXpfxKqhBvSmJlVWpR fnxRaU5q8SFGaQ4WJXFeo2/lKUIC6YklqdmpqQWpRTBZJg5OqQbGDiHuR8daHjzd80HYe++R m74HcwI0leMvfk95v5dzjaWvcYKfyORIlWkWk7MLlcVTYvdmqe5/zzn/QOn8qCXePyfzrlS8 tkZa+RPr76sOi2PC3CwUu25c+Hz7T/W3o56JnAsNa9IuH/BInRQVPDnhZ6BQRZH7ey5WmSMT zFfmOTUwSDV26hsqsRRnJBpqMRcVJwIAH5/Y51wCAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrALMWRmVeSWpSXmKPExsXC5WfdrLst7Uaqwf89mhZz1q9hszg89ySr xeVdc9gs7q35z2pxctZkFot3E76wOrB5LNhU6rF4z0smj02fJrF7nJjxm8Vj8YsPTB6fN8kF sEVx2aSk5mSWpRbp2yVwZdx4c52l4Kl1xe+VcxgbGM/odDFycEgImEhsfC0NYrIIqEqsOBPf xcjJwSagLnHjxk9mEFtEQEPi08Ll7CA2s0CtxOM7M9lAbGGBcImOubtZQWxeAXOJvc0rwGqE BDIlWi7uZoaIC0qcnPmEBaJXS+LGv5dMIKuYBaQllv/jAAlzCthJ/Jp+kxHEFhVQljiw7TjT BEbeWUi6ZyHpnoXQvYCReRWjSGZeWW5iZo6pXnF2RmVeZoVecn7uJkZgOC6r/TNxB+OXy+6H GAU4GJV4eAsSr6cKsSaWFVfmHmKU4GBWEuFlKb+SKsSbklhZlVqUH19UmpNafIhRmoNFSZzX Kzw1QUggPbEkNTs1tSC1CCbLxMEp1cC4KnClRe43Hiv/wD/VvbqhMzYwWF+9Jdifs9l0ttip BV8u1d7o7k6Xfb1ffV9s5wenTav2nuJbdLa35nENyzfzSsUYlm/KfZ+eb2NPUgk481Tx2T+b b/9iJ71g3Mex/F/GN+3LX3sPmTbMCDuqrladXhThG/y7WfSC/Q3DdgHBn5OuFt34IHlZiaU4 I9FQi7moOBEAoRs+N0MCAAA= X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 2A5FB1C0012 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 88snsxrta1qt6rcbf7wu1i4hmxfzmrq6 X-HE-Tag: 1708680891-295516 X-HE-Meta: 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 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: On Fri, Feb 23, 2024 at 05:25:54PM +0800, Huang, Ying wrote: > Byungchul Park writes: > > > 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 05846e34bf02ac9b3e254324dc2d7afd97a025d9 Mon Sep 17 00:00:00 2001 > > From: Byungchul Park > > Date: Fri, 23 Feb 2024 13:47:16 +0900 > > Subject: [PATCH v3] mm, vmscan: do not turn on cache_trim_mode if it doesn't work > > > > With cache_trim_mode on, reclaim logic doesn't bother reclaiming anon > > pages. However, it should be more careful to turn on 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 do not turn on cache_trim_mode if the mode doesn't work, especially > > while the sytem is struggling against 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 | 1636737 | > > | nr_active_anon | 1780700 | 465913 | > > | nr_inactive_file | 30425 | 35711 | > > | nr_active_file | 14961 | 8698 | > > | pgpromote_success | 356 | 1267785 | > > | pgpromote_candidate | 21953245 | 1745631 | > > | pgactivate | 1844523 | 3309867 | > > | pgdeactivate | 50634 | 1545041 | > > | pgfault | 31100294 | 6411036 | > > | pgdemote_kswapd | 30856 | 2267467 | > > | pgscan_kswapd | 1861981 | 7729231 | > > | pgscan_anon | 1822930 | 7667544 | > > | pgscan_file | 39051 | 61687 | > > | pgsteal_anon | 386 | 2227217 | > > | pgsteal_file | 30470 | 40250 | > > | pageoutrun | 30 | 457 | > > | numa_hint_faults | 27418279 | 2752289 | > > | numa_pages_migrated | 356 | 1267785 | > > +-----------------------+-------------------------------+ > > > > Signed-off-by: Byungchul Park > > --- > > mm/vmscan.c | 24 +++++++++++++++++++----- > > 1 file changed, 19 insertions(+), 5 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index bba207f41b14..f7312d831fed 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -127,6 +127,9 @@ struct scan_control { > > /* One of the zones is ready for compaction */ > > unsigned int compaction_ready:1; > > > > + /* If the last try was reclaimable */ > > + unsigned int reclaimable:1; > > + > > /* There is easily reclaimable cold cache in the current node */ > > unsigned int cache_trim_mode:1; > > > > @@ -2266,9 +2269,14 @@ static void prepare_scan_control(pg_data_t *pgdat, struct scan_control *sc) > > * If we have plenty of inactive file pages that aren't > > * thrashing, try to reclaim those first before touching > > * anonymous pages. > > + * > > + * It doesn't make sense to keep cache_trim_mode on if the mode > > + * is not working while struggling against reclaim. So do not > > + * turn it on if so. Note the highest priority of kswapd is 1. > > */ > > 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->cache_trim_mode && !sc->reclaimable && sc->priority <= 1)) > > It's a little hard to digest the logic above for me, is it better to use > the following logic? > > if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE) && > (!sc->cache_trim_mode || sc->reclaimable || sc->priority > 1)) Looks fine to me. Thanks. Byungchul > Otherwise, this looks good to me, feel free to add, > > Acked-by: "Huang, Ying" > > > sc->cache_trim_mode = 1; > > else > > sc->cache_trim_mode = 0; > > @@ -5862,7 +5870,6 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) > > { > > unsigned long nr_reclaimed, nr_scanned, nr_node_reclaimed; > > struct lruvec *target_lruvec; > > - bool reclaimable = false; > > > > if (lru_gen_enabled() && root_reclaim(sc)) { > > lru_gen_shrink_node(pgdat, sc); > > @@ -5877,6 +5884,14 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) > > nr_reclaimed = sc->nr_reclaimed; > > nr_scanned = sc->nr_scanned; > > > > + /* > > + * Reset to the default values at the start. > > + */ > > + if (sc->priority == DEF_PRIORITY) { > > + sc->reclaimable = 1; > > + sc->cache_trim_mode = 0; > > + } > > + > > prepare_scan_control(pgdat, sc); > > > > shrink_node_memcgs(pgdat, sc); > > @@ -5890,8 +5905,7 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) > > vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, > > sc->nr_scanned - nr_scanned, nr_node_reclaimed); > > > > - if (nr_node_reclaimed) > > - reclaimable = true; > > + sc->reclaimable = !!nr_node_reclaimed; > > > > if (current_is_kswapd()) { > > /* > > @@ -5965,7 +5979,7 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) > > * sleep. On reclaim progress, reset the failure counter. A > > * successful direct reclaim run will revive a dormant kswapd. > > */ > > - if (reclaimable) > > + if (sc->reclaimable) > > pgdat->kswapd_failures = 0; > > } > > -- > Best Regards, > Huang, Ying