From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 325043C3F4E; Wed, 16 Sep 2026 22:34:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789598081; cv=none; b=ZDJyW9vhnOMUREIoNHaFd+YpvXu2J/nLDxWfhsqoP/G4SWzlO+QGH/N3VTaEcWE236eyktIF0ki1cSlV3NxnCQKBMOJ8MOsjHwClUpu0HKJ+eFMfn2mX5Is9ERjZT1HqRVjlDNDcNiijcCw6gLUdvWfzTSLWV71c3u/LryngwRE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789598081; c=relaxed/simple; bh=kjav+DCqeVHETk/yTPEOtjQd421No6bIkSUHAp2Uf/8=; h=Date:To:From:Subject:Message-Id; b=t9a3nzFnVSRbKct+BRDXzooYxJvIWmW8LXVAjJJzOZigZEZ/pu3dg23FWw2XmIZ1XyyByJh0ZSDbT9dD1biLbsqJTAl8GxHxKmlNAAVrUzVZ0WreA4wvuvMNNyj3DTm5kcaTTHPIoFO0rsvk3q/hGuzKsmE5I/j7AhOIWgi3Jd4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=m/rR0ri4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="m/rR0ri4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73A331F000FF; Wed, 16 Sep 2026 22:34:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1789598054; bh=ZaNOQQN7Ir5G/SAWmRkWOwnxm+4576UUn38t7oQZkhM=; h=Date:To:From:Subject; b=m/rR0ri4O6YdCUbGkXOqsEvfx1J9qFiH2lqzXbLVkZ/NyT1C4PEQQGSusQDmEBU+8 3SsYR0t7Q8qI8dD15o96fxWYvUOOuLGe99kQPq+0EWOs9QakAJWlPZIj/Wha83E1Dd kHAdwxbHEho0/MVlhPROdkHhH8yXkweW6XDp1O1w= Date: Wed, 16 Sep 2026 15:34:14 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,willy@infradead.org,vbabka@suse.cz,stable@vger.kernel.org,ritesh.list@gmail.com,mhocko@suse.com,hch@lst.de,hannes@cmpxchg.org,dgc@kernel.org,david@redhat.com,dipiets@amazon.it,akpm@linux-foundation.org From: Andrew Morton Subject: [alternative-merged] mm-page_alloc-avoid-direct-compaction-for-costly-__gfp_noretry-allocations-v5.patch removed from -mm tree Message-Id: <20260916223414.73A331F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/page_alloc: avoid direct compaction for costly __GFP_NORETRY allocations has been removed from the -mm tree. Its filename was mm-page_alloc-avoid-direct-compaction-for-costly-__gfp_noretry-allocations-v5.patch This patch was dropped because an alternative patch was or shall be merged ------------------------------------------------------ From: Salvatore Dipietro Subject: mm/page_alloc: avoid direct compaction for costly __GFP_NORETRY allocations Date: Fri, 11 Sep 2026 14:21:02 +0000 Commit 5d8edfb900d5 ("iomap: Copy larger chunks from userspace") introduced high-order folio allocations in the iomap buffered write path. When memory is fragmented, each failed costly-order allocation enters __alloc_pages_slowpath() which runs direct compaction and drain_all_pages(), causing a 0.38x throughput drop on PostgreSQL pgbench (simple-update) with 1024 clients on a 96-vCPU arm64 system. The root issue is that direct compaction is too expensive for hot allocation paths that have fallbacks to smaller allocations. __filemap_get_folio_mpol() already marks higher-order allocations with __GFP_NORETRY | __GFP_NOWARN, signalling that the caller can handle failure. However, the page allocator still attempts full direct compaction for costly orders with __GFP_NORETRY, which is unnecessarily aggressive when the caller will simply retry at a lower order. For costly-order allocations with __GFP_NORETRY, suppress direct reclaim for the whole slowpath by computing can_direct_reclaim (and hence can_compact) as false. The !can_direct_reclaim check near the top of the slowpath then short-circuits to nopage: no direct reclaim, no direct compaction and no drain_all_pages() IPI across every CPU. kswapd (and in turn kcompactd) is still woken further down for background defragmentation, so compaction keeps working for long-term system health while being removed from the latency-critical direct allocation path. Allocations that also request __GFP_THISNODE are exempted. That flag pairing identifies the local-node-first THP attempt issued by alloc_pages_mpol() (mempolicy.c), which relies on direct compaction to form transparent huge pages. __GFP_NOFAIL is exempted as well, so a must-not-fail allocation is never made to fail. Test environment: Hardware: AWS EC2 m8g.24xlarge (96 vCPU, arm64) 12x 1TB IO2 32000 IOPS RAID0 XFS OS: AL2023 Kernel: v7.3-rc1 Database: PostgreSQL 18.4 Workload: pgbench simple-update, 1024 clients, 96 threads, 1200s Results (average of 3 runs, TPS): Config Avg TPS % vs baseline AL2023 stock 6.1 kernel (pre-5d8edfb900d5) 136,942 n/a v7.3-rc1 baseline (no patch) 59,408 - v7.3-rc1 + this patch 161,994 +172.7% The patch fully recovers the pre-5d8edfb900d5 performance, bringing throughput back above the pre-regression level and well clear of the ~59k baseline. The AL2023 6.1 row runs a kernel that predates commit 5d8edfb900d5 ("iomap: Copy larger chunks from userspace"), so it is not directly comparable, but it shows the pre-regression level and confirms that the ~59k baseline is the anomaly and not the norm. Link: https://lore.kernel.org/20260911142102.2294202-1-dipiets@amazon.it Link: https://lore.kernel.org/all/20260403193535.9970-1-dipiets@amazon.it/T/#t [v1] Link: https://lore.kernel.org/linux-mm/20260420161404.642-1-dipiets@amazon.it/T/#u [v2] Link: https://lore.kernel.org/all/20260710143437.12379-1-dipiets@amazon.it/T/#u [v3] Link: https://lore.kernel.org/all/20260904115629.3993331-1-dipiets@amazon.it/T/#u [v4] Fixes: 5d8edfb900d5 ("iomap: Copy larger chunks from userspace") Signed-off-by: Salvatore Dipietro Signed-off-by: Andrew Morton Acked-by: Zi Yan Cc: Vlastimil Babka Cc: David Hildenbrand Cc: Michal Hocko Cc: Johannes Weiner Cc: Matthew Wilcox Cc: Christoph Hellwig Cc: Dave Chinner Cc: Ritesh Harjani Cc: --- mm/page_alloc.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/mm/page_alloc.c~mm-page_alloc-avoid-direct-compaction-for-costly-__gfp_noretry-allocations-v5 +++ a/mm/page_alloc.c @@ -4784,10 +4784,22 @@ static inline struct page * __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, struct alloc_context *ac) { - bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM; + const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER; + /* + * Costly __GFP_NORETRY callers have a cheap fallback to a lower order, + * so don't stall them in direct reclaim or direct compaction. Exempt + * __GFP_THISNODE (the THP attempt from alloc_pages_mpol() needs direct + * compaction) and __GFP_NOFAIL (must not be made to fail). Don't + * clear __GFP_DIRECT_RECLAIM from gfp_mask instead: that would also + * change the alloc_flags derived by alloc_flags_slowpath(). + */ + const bool costly_noretry = costly_order && + (gfp_mask & __GFP_NORETRY) && + !(gfp_mask & (__GFP_THISNODE | __GFP_NOFAIL)); + bool can_direct_reclaim = !costly_noretry && + (gfp_mask & __GFP_DIRECT_RECLAIM); bool can_compact = can_direct_reclaim && gfp_compaction_allowed(gfp_mask); bool nofail = gfp_mask & __GFP_NOFAIL; - const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER; struct page *page = NULL; unsigned int alloc_flags; unsigned long did_some_progress; _ Patches currently in -mm which might be from dipiets@amazon.it are mm-page_alloc-avoid-direct-compaction-for-costly-__gfp_noretry-allocations.patch