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 ADAE84BE450; Wed, 16 Sep 2026 22:34:21 +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=1789598068; cv=none; b=e5hqlKbQ4nsRp6DunamjRj97ttJKOLiZuVqJDjSAs0GwxH4AnzEUPa0kVqhvevFQvEm9s8wLIc26Fy+Dwi7lFMb/U8UoER+JiXIhT5VtA3eIcmzSoMb/k13sP7zFjbrWxFEgYNf5lefOK0OPuowOgaGx/D4NZ0SmF0HOmcdKQVI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789598068; c=relaxed/simple; bh=K3kymkFgsbhoN3JxH0065cn+VEi6TqBVh4l4sn5879g=; h=Date:To:From:Subject:Message-Id; b=aP3D6wCfLDn7w4p+MZsTx1gZeSKozLb3hqliMxMsb4UKYicmFkfkmVhnpFmsNSD1UTCXzJlh+CDAmQrOSjL3PdElF1aULCHcs79hAhr+VfgMYZp0/GN3j1miQv+3/7K9ViljSzh3+ZIu2x0xc9s1ZIcIodrxuXg/Pzy4zUtcUVw= 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=aQd1XDWe; 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="aQd1XDWe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 810961F00893; Wed, 16 Sep 2026 22:34:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1789598058; bh=rqG1hlFDKDAFCEyGhpU+yq15VWWiLqgrt2MlhiWqepQ=; h=Date:To:From:Subject; b=aQd1XDWez9Xi4W3TikZf9dErzaCJcvENlWS1ED4vswmIvio9rjmxomoJucRC3Ddr4 3VcJcQmRhvzhOrda+k1qrFwDpaWa5n1kRipkoGZUT9PliKh16/QrXz2Hfg8n1u+fSl TX4/C5+21HvhIAQqkfCta32Ar0lNKj0U8K6xqg4w= Date: Wed, 16 Sep 2026 15:34:18 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,willy@infradead.org,vbabka@kernel.org,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: + mm-page_alloc-avoid-direct-compaction-for-costly-__gfp_noretry-allocations.patch added to mm-hotfixes-unstable branch Message-Id: <20260916223418.810961F00893@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/page_alloc: avoid direct compaction for costly __GFP_NORETRY allocations has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-page_alloc-avoid-direct-compaction-for-costly-__gfp_noretry-allocations.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-avoid-direct-compaction-for-costly-__gfp_noretry-allocations.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Salvatore Dipietro Subject: mm/page_alloc: avoid direct compaction for costly __GFP_NORETRY allocations Date: Fri, 4 Sep 2026 11:56:28 +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, clear __GFP_DIRECT_RECLAIM at the very start of the slowpath, before can_direct_reclaim, can_compact and the nofail checks are evaluated. This makes the entire slowpath treat the request as non-blocking: 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. 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 baseline (no patch) 59,408 - With this patch 155,409 +161.6% 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/20260904115629.3993331-1-dipiets@amazon.it Fixes: 5d8edfb900d5 ("iomap: Copy larger chunks from userspace") Signed-off-by: Salvatore Dipietro Signed-off-by: Andrew Morton Acked-by: Vlastimil Babka (SUSE) Acked-by: Zi Yan Reviewed-by: Johannes Weiner Reviewed-by: Christoph Hellwig Cc: David Hildenbrand Cc: Michal Hocko Cc: Matthew Wilcox Cc: Dave Chinner Cc: Ritesh Harjani Cc: --- mm/page_alloc.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) --- a/mm/page_alloc.c~mm-page_alloc-avoid-direct-compaction-for-costly-__gfp_noretry-allocations +++ a/mm/page_alloc.c @@ -4784,10 +4784,10 @@ 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; - 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; + bool can_direct_reclaim; + bool can_compact; + bool nofail; struct page *page = NULL; unsigned int alloc_flags; unsigned long did_some_progress; @@ -4802,6 +4802,18 @@ __alloc_pages_slowpath(gfp_t gfp_mask, u bool can_retry_reserves = true; unsigned long alloc_start_time = jiffies; + /* + * Costly __GFP_NORETRY callers have a cheap fallback, so don't stall + * them in reclaim or compaction. __GFP_THISNODE callers are exempt. + */ + if (costly_order && (gfp_mask & __GFP_NORETRY) && + !(gfp_mask & __GFP_THISNODE)) + gfp_mask &= ~__GFP_DIRECT_RECLAIM; + + can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM; + can_compact = can_direct_reclaim && gfp_compaction_allowed(gfp_mask); + nofail = gfp_mask & __GFP_NOFAIL; + if (unlikely(nofail)) { /* * Also we don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM, _ Patches currently in -mm which might be from dipiets@amazon.it are mm-page_alloc-avoid-direct-compaction-for-costly-__gfp_noretry-allocations.patch