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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35E4CC10F04 for ; Fri, 8 Dec 2023 06:14:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233153AbjLHGOQ (ORCPT ); Fri, 8 Dec 2023 01:14:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53482 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229801AbjLHGOK (ORCPT ); Fri, 8 Dec 2023 01:14:10 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2EC5E171F for ; Thu, 7 Dec 2023 22:14:16 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id 3f1490d57ef6-db548f8dae4so2294059276.3 for ; Thu, 07 Dec 2023 22:14:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1702016055; x=1702620855; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=MPyzSKrXH5Tqmu9fHEEk3D/5egUUX9zjhxgsMiAOvSY=; b=sx41H2WPZze9RWflhBXz/lSSAEC3LY0JnjR3LOlOzXrnPNvP8f6bQZVip5xKRq78kE jeyVo9r+Whn7Hz9qv0N/oel3byRyL53qMpC7gU+4o1KeK2CpB3Gq3Lo4VAQnqJvOnvrC KmlB3msz8cfcEqQWI7QXMuzZgt8OlwQLdhinMKYFshrAOrsYTEfdMK1F8yR3krsomZxx YXp21SOKcabj2Ogkkhg8IsF/fh95K92d3TNvuk8yQJA7B/B5ea+HVKUKy28hRVSLyHjD lynMy5FeiiLCkulYVtLNOi7E/70+EHF3uRcT5fRsjG6sCqa0TAFASwrJw3FaKzI+t+AN l2pg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702016055; x=1702620855; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=MPyzSKrXH5Tqmu9fHEEk3D/5egUUX9zjhxgsMiAOvSY=; b=ukKenaKztEtDF5WHhWHmc39/+O1jyqnNBpkBVUe2YpxXdHsJce8dr3P8Uyc0wN5QQY 7gV63Tpx4QesTfyUsQTjuEamMLo1/5TFSSjHcIUAw/gpDqu045m7qqCxfGmMrqDp/v4F ZRu821kQ/XKLvMYROg0p08kcwwkFPx0xnGe8AkeSFtPndXicxm7u5uPJjKCloaVskAXt 8u1DqgF4fBbG7QuAua41JVsVRFmF6B8c9zsIFifje1F0BiygHr7h+XnzXhAW2WL0pw6M SadihBO//PLtY2u32c+75MkEEEjlTv4HxoJfLjrlbXMs7fJQ5Fs2pkiELEC+wzkumeu4 Tsxw== X-Gm-Message-State: AOJu0YzeITMglcSsVzBvzrZpzPcVEsYmsudj0w0EXpB9YIi5YY0aEYPE hnWY4UV3k57OmCzTNfaR1h26HjyUv9M= X-Google-Smtp-Source: AGHT+IGdRJ6oJBGbszEwYJdNZWMiTiNDeQOA8ujBPwzvHJj4q8s9r2Akp7Hq9nIVYDsXPZgw2A9/YR7iKD4= X-Received: from yuzhao2.bld.corp.google.com ([100.64.188.49]) (user=yuzhao job=sendgmr) by 2002:a25:76d5:0:b0:da0:3da9:ce08 with SMTP id r204-20020a2576d5000000b00da03da9ce08mr52921ybc.10.1702016055395; Thu, 07 Dec 2023 22:14:15 -0800 (PST) Date: Thu, 7 Dec 2023 23:14:05 -0700 In-Reply-To: <20231208061407.2125867-1-yuzhao@google.com> Mime-Version: 1.0 References: <20231208061407.2125867-1-yuzhao@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231208061407.2125867-2-yuzhao@google.com> Subject: [PATCH mm-unstable v1 2/4] mm/mglru: try to stop at high watermarks From: Yu Zhao To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yu Zhao , Charan Teja Kalla , Jaroslav Pulchart , Kalesh Singh , stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The initial MGLRU patchset didn't include the memcg LRU support, and it relied on should_abort_scan(), added by commit f76c83378851 ("mm: multi-gen LRU: optimize multiple memcgs"), to "backoff to avoid overshooting their aggregate reclaim target by too much". Later on when the memcg LRU was added, should_abort_scan() was deemed unnecessary, and the test results [1] showed no side effects after it was removed by commit a579086c99ed ("mm: multi-gen LRU: remove eviction fairness safeguard"). However, that test used memory.reclaim, which sets nr_to_reclaim to SWAP_CLUSTER_MAX. So it can overshoot only by SWAP_CLUSTER_MAX-1 pages, i.e., from nr_reclaimed=nr_to_reclaim-1 to nr_reclaimed=nr_to_reclaim+SWAP_CLUSTER_MAX-1. Compared with the batch size kswapd sets to nr_to_reclaim, SWAP_CLUSTER_MAX is tiny. Therefore that test isn't able to reproduce the worst case scenario, i.e., kswapd overshooting GBs on large systems and "consuming 100% CPU" (see the Closes tag). Bring back a simplified version of should_abort_scan() on top of the memcg LRU, so that kswapd stops when all eligible zones are above their respective high watermarks plus a small delta to lower the chance of KSWAPD_HIGH_WMARK_HIT_QUICKLY. Note that this only applies to order-0 reclaim, meaning compaction-induced reclaim can still run wild (which is a different problem). On Android, launching 55 apps sequentially: Before After Change pgpgin 838377172 802955040 -4% pgpgout 38037080 34336300 -10% [1] https://lore.kernel.org/20221222041905.2431096-1-yuzhao@google.com/ Fixes: a579086c99ed ("mm: multi-gen LRU: remove eviction fairness safeguard") Signed-off-by: Yu Zhao Reported-by: Charan Teja Kalla Reported-by: Jaroslav Pulchart Closes: https://lore.kernel.org/CAK8fFZ4DY+GtBA40Pm7Nn5xCHy+51w3sfxPqkqpqakSXYyX+Wg@mail.gmail.com/ Tested-by: Jaroslav Pulchart Tested-by: Kalesh Singh Cc: stable@vger.kernel.org --- mm/vmscan.c | 36 ++++++++++++++++++++++++++++-------- 1 file changed, 28 insertions(+), 8 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index e67631c60ac0..10e964cd0efe 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4676,20 +4676,41 @@ static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool return try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false) ? -1 : 0; } -static unsigned long get_nr_to_reclaim(struct scan_control *sc) +static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc) { + int i; + enum zone_watermarks mark; + /* don't abort memcg reclaim to ensure fairness */ if (!root_reclaim(sc)) - return -1; + return false; - return max(sc->nr_to_reclaim, compact_gap(sc->order)); + if (sc->nr_reclaimed >= max(sc->nr_to_reclaim, compact_gap(sc->order))) + return true; + + /* check the order to exclude compaction-induced reclaim */ + if (!current_is_kswapd() || sc->order) + return false; + + mark = sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING ? + WMARK_PROMO : WMARK_HIGH; + + for (i = 0; i <= sc->reclaim_idx; i++) { + struct zone *zone = lruvec_pgdat(lruvec)->node_zones + i; + unsigned long size = wmark_pages(zone, mark) + MIN_LRU_BATCH; + + if (managed_zone(zone) && !zone_watermark_ok(zone, 0, size, sc->reclaim_idx, 0)) + return false; + } + + /* kswapd should abort if all eligible zones are safe */ + return true; } static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) { long nr_to_scan; unsigned long scanned = 0; - unsigned long nr_to_reclaim = get_nr_to_reclaim(sc); int swappiness = get_swappiness(lruvec, sc); /* clean file folios are more likely to exist */ @@ -4711,7 +4732,7 @@ static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) if (scanned >= nr_to_scan) break; - if (sc->nr_reclaimed >= nr_to_reclaim) + if (should_abort_scan(lruvec, sc)) break; cond_resched(); @@ -4772,7 +4793,6 @@ static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc) struct lru_gen_folio *lrugen; struct mem_cgroup *memcg; const struct hlist_nulls_node *pos; - unsigned long nr_to_reclaim = get_nr_to_reclaim(sc); bin = first_bin = get_random_u32_below(MEMCG_NR_BINS); restart: @@ -4805,7 +4825,7 @@ static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc) rcu_read_lock(); - if (sc->nr_reclaimed >= nr_to_reclaim) + if (should_abort_scan(lruvec, sc)) break; } @@ -4816,7 +4836,7 @@ static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc) mem_cgroup_put(memcg); - if (sc->nr_reclaimed >= nr_to_reclaim) + if (!is_a_nulls(pos)) return; /* restart if raced with lru_gen_rotate_memcg() */ -- 2.43.0.472.g3155946c3a-goog