From patchwork Wed Apr 5 18:54:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 13202372 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 2F4B3C76188 for ; Wed, 5 Apr 2023 18:54:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234373AbjDESyf (ORCPT ); Wed, 5 Apr 2023 14:54:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49204 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234354AbjDESyd (ORCPT ); Wed, 5 Apr 2023 14:54:33 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69A196187 for ; Wed, 5 Apr 2023 11:54:32 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 8-20020a250508000000b00b7c653a0a4aso28804603ybf.23 for ; Wed, 05 Apr 2023 11:54:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1680720871; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=oB2sMXwt0v6x8lwXtmYlxh/hoioeozIJIVJcuuQJKWA=; b=Ros0vevjUiwI3/TjUKg+KCeA5SHnfksHcC4OK3M0Fn4fXpXuUrynI6b8MaR9/c3jSk kYtK4Ske7kxweFphiQTIVIVAbS/Fuv7jZA8Wq1GWNo0oxzQ5Nh5pojz9jDp+do2ph3Jj IztRjzkxwy2vWa3oGo525fcM6H4ZEmqQU6p4rYHtfJsYsBqy2LUHEZvuMUuNIKTo/uqK Xwb0LLWXZaQYVo8lUIEKsrrCdSMMCxNVxpuQ+1xdxcKxOZL6ys2NO41rWyag1l5oLhzt LVX/O/QEV66s0ajoxgyOizIIfKMnIekWa445aOdc74s+Q8ItuYHAsLFXOFgFRUjGTZ12 4y1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680720871; 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=oB2sMXwt0v6x8lwXtmYlxh/hoioeozIJIVJcuuQJKWA=; b=1H7G3MPeM0COrf1aVQ9LWJSozY7mH8dbRfhYOWXZhDZAMpLGsvR9kHovQU5GuQdSte W1mq0IsbKktbNVZY3FZhbXhihG/uM8vCUxEzJFvabNWs7lh7tAqzrgzi+I/mhb/3nCJW znTK+H0yjTuUz0I7N3wUG77ArdbZOxZ1uQjrc0Q41BKVa9eaYUABHNeXnj21akC3zY8O m1TFEvID59mHPTO1p4sG2pmX3EDz0k/FeXfhn7AXkJBjr+GvgSFo+qdpEdseptUwgy+q RMjtTADJCOGvNitteJ10NvMpfJmrA/2ZA84OtQgprMy+LKy3cBh8AQWG0vTvTCpWywvc ARqQ== X-Gm-Message-State: AAQBX9c7hy7MQ4EkhVvwVu5G6xXbMeNtrw6RMPYojM/z19kNH2MXKCrV 1FwkdvSx9SmBiA2PBxqbkOip4Z5q9i+kjL3W X-Google-Smtp-Source: AKy350ZCAIete9IDtcJDwB8xbNQZBALRdtx0fEvZ0QLo3PyT+UesbYmBb8Uc0roxQG5ktSucSqhPRJ3viu7kH1ie X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a25:d986:0:b0:b8b:eea7:525c with SMTP id q128-20020a25d986000000b00b8beea7525cmr163875ybg.9.1680720871655; Wed, 05 Apr 2023 11:54:31 -0700 (PDT) Date: Wed, 5 Apr 2023 18:54:26 +0000 In-Reply-To: <20230405185427.1246289-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230405185427.1246289-1-yosryahmed@google.com> X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <20230405185427.1246289-2-yosryahmed@google.com> Subject: [PATCH v5 1/2] mm: vmscan: ignore non-LRU-based reclaim in memcg reclaim From: Yosry Ahmed To: Andrew Morton , Alexander Viro , "Darrick J. Wong" , Christoph Lameter , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Matthew Wilcox (Oracle)" , Miaohe Lin , David Hildenbrand , Johannes Weiner , Peter Xu , NeilBrown , Shakeel Butt , Michal Hocko , Yu Zhao , Dave Chinner Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Yosry Ahmed , stable@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org We keep track of different types of reclaimed pages through reclaim_state->reclaimed_slab, and we add them to the reported number of reclaimed pages. For non-memcg reclaim, this makes sense. For memcg reclaim, we have no clue if those pages are charged to the memcg under reclaim. Slab pages are shared by different memcgs, so a freed slab page may have only been partially charged to the memcg under reclaim. The same goes for clean file pages from pruned inodes (on highmem systems) or xfs buffer pages, there is no simple way to currently link them to the memcg under reclaim. Stop reporting those freed pages as reclaimed pages during memcg reclaim. This should make the return value of writing to memory.reclaim, and may help reduce unnecessary reclaim retries during memcg charging. Writing to memory.reclaim on the root memcg is considered as cgroup_reclaim(), but for this case we want to include any freed pages, so use the global_reclaim() check instead of !cgroup_reclaim(). Generally, this should make the return value of try_to_free_mem_cgroup_pages() more accurate. In some limited cases (e.g. freed a slab page that was mostly charged to the memcg under reclaim), the return value of try_to_free_mem_cgroup_pages() can be underestimated, but this should be fine. The freed pages will be uncharged anyway, and we can charge the memcg the next time around as we usually do memcg reclaim in a retry loop. The next patch performs some cleanups around reclaim_state and adds an elaborate comment explaining this to the code. This patch is kept minimal for easy backporting. Signed-off-by: Yosry Ahmed Cc: stable@vger.kernel.org --- global_reclaim(sc) does not exist in kernels before 6.3. It can be replaced with: !cgroup_reclaim(sc) || mem_cgroup_is_root(sc->target_mem_cgroup) --- mm/vmscan.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 9c1c5e8b24b8f..c82bd89f90364 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -5346,8 +5346,10 @@ static int shrink_one(struct lruvec *lruvec, struct scan_control *sc) vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned, sc->nr_reclaimed - reclaimed); - sc->nr_reclaimed += current->reclaim_state->reclaimed_slab; - current->reclaim_state->reclaimed_slab = 0; + if (global_reclaim(sc)) { + sc->nr_reclaimed += current->reclaim_state->reclaimed_slab; + current->reclaim_state->reclaimed_slab = 0; + } return success ? MEMCG_LRU_YOUNG : 0; } @@ -6472,7 +6474,7 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) shrink_node_memcgs(pgdat, sc); - if (reclaim_state) { + if (reclaim_state && global_reclaim(sc)) { sc->nr_reclaimed += reclaim_state->reclaimed_slab; reclaim_state->reclaimed_slab = 0; } From patchwork Wed Apr 5 18:54:27 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yosry Ahmed X-Patchwork-Id: 13202373 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 A34FEC7619A for ; Wed, 5 Apr 2023 18:54:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230114AbjDESyn (ORCPT ); Wed, 5 Apr 2023 14:54:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49452 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234329AbjDESyi (ORCPT ); Wed, 5 Apr 2023 14:54:38 -0400 Received: from mail-pf1-x449.google.com (mail-pf1-x449.google.com [IPv6:2607:f8b0:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AB4E561B6 for ; Wed, 5 Apr 2023 11:54:33 -0700 (PDT) Received: by mail-pf1-x449.google.com with SMTP id a6-20020aa795a6000000b006262c174d64so16443433pfk.7 for ; Wed, 05 Apr 2023 11:54:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1680720873; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=4yIEsCxGxp+Goi3FcKFGmOxdWE8VaKQI4GXE/OXZVyU=; b=TF78184WybJytfdYm4GCjpWzSx4mUisBexI8bJfnyd6K4JeOX369L2ClHVn4Ys8I7V JV+y1m7UAB4SCcuHTJGFIgQF6+zPgKdblexEZW4hF8aKIUP946k53euPlWdSC0diJGII +4BQZqOlikwwOc1ffTqbrRHhEVpr3wXhWZ0WF/Lu4nUjgmKclpwmru3gluXbSweQuK7W C3JM5wV7WTynZX48f/Lp4lcdapj5Vg97KMACQe2OSnlckxh/DO5uCHLUHH1nrwiXFUnK JKlKgk5qWcBAj572MmVExUzKlzT1AeS/W+Ao4ZB3tIG21TaLoaVVgW0UNpmmTPc769jm okiw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680720873; 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=4yIEsCxGxp+Goi3FcKFGmOxdWE8VaKQI4GXE/OXZVyU=; b=09EvEu5Y7d5/aNHL9WvDZ1d5bvOrX+xsBYVtQ1cjsrPj2CvNEegZVtjJucR0L6YUWU oeX/00p++2vQ7mscJssU4Mk2pa0ZEnBSybp6bWCliHAG128429dTUSW8yrwjeAZngKDF M0YsnePdRl6TS53NqWo5aYxZqAj634YD7afXBXEY+RloTYcAh1VnclAh6y8E8JNCsuxW jumot2tBYx4vreQLrx8DLwsJuRiABX6TRzrKrX+IN2zL9WPS7XDGu5Xxy4Rdyk2HtDqO cru7Qe+gIQvXwS/jmV+0HWrvXVhP1aEbq624+z4kJGANNvWhGYbP3MIWm4XAmwRynvN5 0vcQ== X-Gm-Message-State: AAQBX9fpYri0yZI3lfef+4PIN2T8wePqL3IujIAzO0ITLukCETH29U/D bNYFNHCXjKvy3soupkZsdtQGMA9r/uQg1zRY X-Google-Smtp-Source: AKy350acXJNtGWroYsn6aFMZG+1teLm2kBpgOPT0A7iZ6zD9rHb+p4s9om4KF91yo2bhBQ0j07DSjkYPZ7RoOPdC X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a05:6a00:2da6:b0:625:ccea:1627 with SMTP id fb38-20020a056a002da600b00625ccea1627mr3896876pfb.5.1680720873145; Wed, 05 Apr 2023 11:54:33 -0700 (PDT) Date: Wed, 5 Apr 2023 18:54:27 +0000 In-Reply-To: <20230405185427.1246289-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230405185427.1246289-1-yosryahmed@google.com> X-Mailer: git-send-email 2.40.0.348.gf938b09366-goog Message-ID: <20230405185427.1246289-3-yosryahmed@google.com> Subject: [PATCH v5 2/2] mm: vmscan: refactor reclaim_state helpers From: Yosry Ahmed To: Andrew Morton , Alexander Viro , "Darrick J. Wong" , Christoph Lameter , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Matthew Wilcox (Oracle)" , Miaohe Lin , David Hildenbrand , Johannes Weiner , Peter Xu , NeilBrown , Shakeel Butt , Michal Hocko , Yu Zhao , Dave Chinner Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Yosry Ahmed Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org During reclaim, we keep track of pages reclaimed from other means than LRU-based reclaim through scan_control->reclaim_state->reclaimed_slab, which we stash a pointer to in current task_struct. However, we keep track of more than just reclaimed slab pages through this. We also use it for clean file pages dropped through pruned inodes, and xfs buffer pages freed. Rename reclaimed_slab to reclaimed, and add a helper function that wraps updating it through current, so that future changes to this logic are contained within mm/vmscan.c. Additionally, add a flush_reclaim_state() helper to wrap using reclaim_state->reclaimed to updated sc->nr_reclaimed, and use that helper to add an elaborate comment about why we only do the update for global reclaim. Finally, move set_task_reclaim_state() next to flush_reclaim_state() so that all reclaim_state helpers are in close proximity for easier readability. Signed-off-by: Yosry Ahmed --- fs/inode.c | 3 +- fs/xfs/xfs_buf.c | 3 +- include/linux/swap.h | 17 +++++++++- mm/slab.c | 3 +- mm/slob.c | 6 ++-- mm/slub.c | 5 ++- mm/vmscan.c | 75 ++++++++++++++++++++++++++++++++------------ 7 files changed, 78 insertions(+), 34 deletions(-) diff --git a/fs/inode.c b/fs/inode.c index 4558dc2f13557..e60fcc41faf17 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -864,8 +864,7 @@ static enum lru_status inode_lru_isolate(struct list_head *item, __count_vm_events(KSWAPD_INODESTEAL, reap); else __count_vm_events(PGINODESTEAL, reap); - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += reap; + mm_account_reclaimed_pages(reap); } iput(inode); spin_lock(lru_lock); diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c index 54c774af6e1c6..15d1e5a7c2d34 100644 --- a/fs/xfs/xfs_buf.c +++ b/fs/xfs/xfs_buf.c @@ -286,8 +286,7 @@ xfs_buf_free_pages( if (bp->b_pages[i]) __free_page(bp->b_pages[i]); } - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += bp->b_page_count; + mm_account_reclaimed_pages(bp->b_page_count); if (bp->b_pages != bp->b_page_array) kmem_free(bp->b_pages); diff --git a/include/linux/swap.h b/include/linux/swap.h index 209a425739a9f..e131ac155fb95 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -153,13 +153,28 @@ union swap_header { * memory reclaim */ struct reclaim_state { - unsigned long reclaimed_slab; + /* pages reclaimed outside of LRU-based reclaim */ + unsigned long reclaimed; #ifdef CONFIG_LRU_GEN /* per-thread mm walk data */ struct lru_gen_mm_walk *mm_walk; #endif }; +/* + * mm_account_reclaimed_pages(): account reclaimed pages outside of LRU-based + * reclaim + * @pages: number of pages reclaimed + * + * If the current process is undergoing a reclaim operation, increment the + * number of reclaimed pages by @pages. + */ +static inline void mm_account_reclaimed_pages(unsigned long pages) +{ + if (current->reclaim_state) + current->reclaim_state->reclaimed += pages; +} + #ifdef __KERNEL__ struct address_space; diff --git a/mm/slab.c b/mm/slab.c index dabc2a671fc6f..64bf1de817b24 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -1392,8 +1392,7 @@ static void kmem_freepages(struct kmem_cache *cachep, struct slab *slab) smp_wmb(); __folio_clear_slab(folio); - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += 1 << order; + mm_account_reclaimed_pages(1 << order); unaccount_slab(slab, order, cachep); __free_pages(&folio->page, order); } diff --git a/mm/slob.c b/mm/slob.c index fe567fcfa3a39..79cc8680c973c 100644 --- a/mm/slob.c +++ b/mm/slob.c @@ -61,7 +61,7 @@ #include #include -#include /* struct reclaim_state */ +#include /* mm_account_reclaimed_pages() */ #include #include #include @@ -211,9 +211,7 @@ static void slob_free_pages(void *b, int order) { struct page *sp = virt_to_page(b); - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += 1 << order; - + mm_account_reclaimed_pages(1 << order); mod_node_page_state(page_pgdat(sp), NR_SLAB_UNRECLAIMABLE_B, -(PAGE_SIZE << order)); __free_pages(sp, order); diff --git a/mm/slub.c b/mm/slub.c index 39327e98fce34..7aa30eef82350 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -11,7 +11,7 @@ */ #include -#include /* struct reclaim_state */ +#include /* mm_account_reclaimed_pages() */ #include #include #include @@ -2063,8 +2063,7 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab) /* Make the mapping reset visible before clearing the flag */ smp_wmb(); __folio_clear_slab(folio); - if (current->reclaim_state) - current->reclaim_state->reclaimed_slab += pages; + mm_account_reclaimed_pages(pages); unaccount_slab(slab, order, s); __free_pages(&folio->page, order); } diff --git a/mm/vmscan.c b/mm/vmscan.c index c82bd89f90364..049e39202e6ce 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -188,18 +188,6 @@ struct scan_control { */ int vm_swappiness = 60; -static void set_task_reclaim_state(struct task_struct *task, - struct reclaim_state *rs) -{ - /* Check for an overwrite */ - WARN_ON_ONCE(rs && task->reclaim_state); - - /* Check for the nulling of an already-nulled member */ - WARN_ON_ONCE(!rs && !task->reclaim_state); - - task->reclaim_state = rs; -} - LIST_HEAD(shrinker_list); DECLARE_RWSEM(shrinker_rwsem); @@ -511,6 +499,59 @@ static bool writeback_throttling_sane(struct scan_control *sc) } #endif +static void set_task_reclaim_state(struct task_struct *task, + struct reclaim_state *rs) +{ + /* Check for an overwrite */ + WARN_ON_ONCE(rs && task->reclaim_state); + + /* Check for the nulling of an already-nulled member */ + WARN_ON_ONCE(!rs && !task->reclaim_state); + + task->reclaim_state = rs; +} + +/* + * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to + * scan_control->nr_reclaimed. + */ +static void flush_reclaim_state(struct scan_control *sc, + struct reclaim_state *rs) +{ + /* + * Currently, reclaim_state->reclaimed includes three types of pages + * freed outside of vmscan: + * (1) Slab pages. + * (2) Clean file pages from pruned inodes. + * (3) XFS freed buffer pages. + * + * For all of these cases, we have no way of finding out whether these + * pages were related to the memcg under reclaim. For example, a freed + * slab page could have had only a single object charged to the memcg + * under reclaim. Also, populated inodes are not on shrinker LRUs + * anymore except on highmem systems. + * + * Instead of over-reporting the reclaimed pages in a memcg reclaim, + * only count such pages in global reclaim. This prevents unnecessary + * retries during memcg charging and false positive from proactive + * reclaim (memory.reclaim). + * + * For uncommon cases were the freed pages were actually significantly + * charged to the memcg under reclaim, and we end up under-reporting, it + * should be fine. The freed pages will be uncharged anyway, even if + * they are not reported properly, and we will be able to make forward + * progress in charging (which is usually in a retry loop). + * + * We can go one step further, and report the uncharged objcg pages in + * memcg reclaim, to make reporting more accurate and reduce + * under-reporting, but it's probably not worth the complexity for now. + */ + if (rs && global_reclaim(sc)) { + sc->nr_reclaimed += rs->reclaimed; + rs->reclaimed = 0; + } +} + static long xchg_nr_deferred(struct shrinker *shrinker, struct shrink_control *sc) { @@ -5346,10 +5387,7 @@ static int shrink_one(struct lruvec *lruvec, struct scan_control *sc) vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned, sc->nr_reclaimed - reclaimed); - if (global_reclaim(sc)) { - sc->nr_reclaimed += current->reclaim_state->reclaimed_slab; - current->reclaim_state->reclaimed_slab = 0; - } + flush_reclaim_state(sc, current->reclaim_state); return success ? MEMCG_LRU_YOUNG : 0; } @@ -6474,10 +6512,7 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) shrink_node_memcgs(pgdat, sc); - if (reclaim_state && global_reclaim(sc)) { - sc->nr_reclaimed += reclaim_state->reclaimed_slab; - reclaim_state->reclaimed_slab = 0; - } + flush_reclaim_state(sc, reclaim_state); /* Record the subtree's reclaim efficiency */ if (!sc->proactive)