From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A756C101DE; Mon, 16 Dec 2024 05:19:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734326398; cv=none; b=U+9GtUDVRyLf3YvaD3fanwpgQkIYiJLwPtwWecOhrpV7C1/nymgzr6aFhCTBVLsRXm7xQiJ7l4cvsGjhcYYMAMBhm4OeFWn4F79WBUK1n5KGVo91UA1gWRQ20k+Rw5s3QOfz70K/5MjZ+x2bJOGesVnizsseg0gujbEkIMhQQfo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734326398; c=relaxed/simple; bh=icacqnachTe38ZTd6yONyOo/ht5NIHsCSc4yyu7t3EI=; h=Date:To:From:Subject:Message-Id; b=ewoPpkK2uBkPnSzg0PH8CLEL2kXxhTlVshuz0YwU6dKPQacPtIGj5rq4g86YXZunuxRwMiGB7/iNXmrW6SySBvvhGy2huEEKFB1b9BZl1Qo7GxEzQMEaeX0PCiYWQzFbohb3CACiV3d7quvurrCddqfR9R5YRwwqJIv/7aUu4AM= 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=tFLv2l8w; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="tFLv2l8w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 10F2AC4CED0; Mon, 16 Dec 2024 05:19:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1734326398; bh=icacqnachTe38ZTd6yONyOo/ht5NIHsCSc4yyu7t3EI=; h=Date:To:From:Subject:From; b=tFLv2l8w/MxfXz3X87bntof5ANXjAkdWsDEtqX0+uzFwDJFUOlK7aX4rwswWJJQCa ZO0vI0klUbla/jygut5y3ZWSSdhB36F4HSByiF60r6uelOM6D/2cMgD3yAJnnwyGUO EeY+yCWC5gessg8h84jUcOqOoz1zp7MRgfGOghI0= Date: Sun, 15 Dec 2024 21:19:57 -0800 To: mm-commits@vger.kernel.org,vbabka@suse.cz,stable@vger.kernel.org,david@redhat.com,baolin.wang@linux.alibaba.com,yangge1116@126.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-compaction-dont-use-alloc_cma-in-long-term-gup-flow.patch added to mm-hotfixes-unstable branch Message-Id: <20241216051958.10F2AC4CED0@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm, compaction: don't use ALLOC_CMA in long term GUP flow has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-compaction-dont-use-alloc_cma-in-long-term-gup-flow.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-compaction-dont-use-alloc_cma-in-long-term-gup-flow.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 the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: yangge Subject: mm, compaction: don't use ALLOC_CMA in long term GUP flow Date: Sun, 15 Dec 2024 18:01:07 +0800 Since commit 984fdba6a32e ("mm, compaction: use proper alloc_flags in __compaction_suitable()") allow compaction to proceed when free pages required for compaction reside in the CMA pageblocks, it's possible that __compaction_suitable() always returns true, and in some cases, it's not acceptable. There are 4 NUMA nodes on my machine, and each NUMA node has 32GB of memory. I have configured 16GB of CMA memory on each NUMA node, and starting a 32GB virtual machine with device passthrough is extremely slow, taking almost an hour. During the start-up of the virtual machine, it will call pin_user_pages_remote(..., FOLL_LONGTERM, ...) to allocate memory. Long term GUP cannot allocate memory from CMA area, so a maximum of 16 GB of no-CMA memory on a NUMA node can be used as virtual machine memory. Since there is 16G of free CMA memory on the NUMA node, watermark for order-0 always be met for compaction, so __compaction_suitable() always returns true, even if the node is unable to allocate non-CMA memory for the virtual machine. For costly allocations, because __compaction_suitable() always returns true, __alloc_pages_slowpath() can't exit at the appropriate place, resulting in excessively long virtual machine startup times. Call trace: __alloc_pages_slowpath if (compact_result == COMPACT_SKIPPED || compact_result == COMPACT_DEFERRED) goto nopage; // should exit __alloc_pages_slowpath() from here In order to quickly fall back to remote node, we should remove ALLOC_CMA both in __compaction_suitable() and __isolate_free_page() in long term GUP flow. After this fix, starting a 32GB virtual machine with device passthrough takes only a few seconds. Link: https://lkml.kernel.org/r/1734256867-19614-1-git-send-email-yangge1116@126.com Fixes: 984fdba6a32e ("mm, compaction: use proper alloc_flags in __compaction_suitable()") Signed-off-by: yangge Cc: Baolin Wang Cc: David Hildenbrand Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton --- include/linux/compaction.h | 6 ++++-- mm/compaction.c | 18 +++++++++++------- mm/page_alloc.c | 4 +++- mm/vmscan.c | 4 ++-- 4 files changed, 20 insertions(+), 12 deletions(-) --- a/include/linux/compaction.h~mm-compaction-dont-use-alloc_cma-in-long-term-gup-flow +++ a/include/linux/compaction.h @@ -90,7 +90,8 @@ extern enum compact_result try_to_compac struct page **page); extern void reset_isolation_suitable(pg_data_t *pgdat); extern bool compaction_suitable(struct zone *zone, int order, - int highest_zoneidx); + int highest_zoneidx, + unsigned int alloc_flags); extern void compaction_defer_reset(struct zone *zone, int order, bool alloc_success); @@ -108,7 +109,8 @@ static inline void reset_isolation_suita } static inline bool compaction_suitable(struct zone *zone, int order, - int highest_zoneidx) + int highest_zoneidx, + unsigned int alloc_flags) { return false; } --- a/mm/compaction.c~mm-compaction-dont-use-alloc_cma-in-long-term-gup-flow +++ a/mm/compaction.c @@ -2379,9 +2379,11 @@ static enum compact_result compact_finis static bool __compaction_suitable(struct zone *zone, int order, int highest_zoneidx, + unsigned int alloc_flags, unsigned long wmark_target) { unsigned long watermark; + bool use_cma; /* * Watermarks for order-0 must be met for compaction to be able to * isolate free pages for migration targets. This means that the @@ -2393,25 +2395,27 @@ static bool __compaction_suitable(struct * even if compaction succeeds. * For costly orders, we require low watermark instead of min for * compaction to proceed to increase its chances. - * ALLOC_CMA is used, as pages in CMA pageblocks are considered - * suitable migration targets + * In addition to long term GUP flow, ALLOC_CMA is used, as pages in + * CMA pageblocks are considered suitable migration targets */ watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ? low_wmark_pages(zone) : min_wmark_pages(zone); watermark += compact_gap(order); + use_cma = !!(alloc_flags & ALLOC_CMA); return __zone_watermark_ok(zone, 0, watermark, highest_zoneidx, - ALLOC_CMA, wmark_target); + use_cma ? ALLOC_CMA : 0, wmark_target); } /* * compaction_suitable: Is this suitable to run compaction on this zone now? */ -bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx) +bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx, + unsigned int alloc_flags) { enum compact_result compact_result; bool suitable; - suitable = __compaction_suitable(zone, order, highest_zoneidx, + suitable = __compaction_suitable(zone, order, highest_zoneidx, alloc_flags, zone_page_state(zone, NR_FREE_PAGES)); /* * fragmentation index determines if allocation failures are due to @@ -2472,7 +2476,7 @@ bool compaction_zonelist_suitable(struct available = zone_reclaimable_pages(zone) / order; available += zone_page_state_snapshot(zone, NR_FREE_PAGES); if (__compaction_suitable(zone, order, ac->highest_zoneidx, - available)) + alloc_flags, available)) return true; } @@ -2497,7 +2501,7 @@ compaction_suit_allocation_order(struct alloc_flags)) return COMPACT_SUCCESS; - if (!compaction_suitable(zone, order, highest_zoneidx)) + if (!compaction_suitable(zone, order, highest_zoneidx, alloc_flags)) return COMPACT_SKIPPED; return COMPACT_CONTINUE; --- a/mm/page_alloc.c~mm-compaction-dont-use-alloc_cma-in-long-term-gup-flow +++ a/mm/page_alloc.c @@ -2812,6 +2812,7 @@ int __isolate_free_page(struct page *pag { struct zone *zone = page_zone(page); int mt = get_pageblock_migratetype(page); + bool pin; if (!is_migrate_isolate(mt)) { unsigned long watermark; @@ -2822,7 +2823,8 @@ int __isolate_free_page(struct page *pag * exists. */ watermark = zone->_watermark[WMARK_MIN] + (1UL << order); - if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA)) + pin = !!(current->flags & PF_MEMALLOC_PIN); + if (!zone_watermark_ok(zone, 0, watermark, 0, pin ? 0 : ALLOC_CMA)) return 0; } --- a/mm/vmscan.c~mm-compaction-dont-use-alloc_cma-in-long-term-gup-flow +++ a/mm/vmscan.c @@ -5861,7 +5861,7 @@ static inline bool should_continue_recla sc->reclaim_idx, 0)) return false; - if (compaction_suitable(zone, sc->order, sc->reclaim_idx)) + if (compaction_suitable(zone, sc->order, sc->reclaim_idx, ALLOC_CMA)) return false; } @@ -6089,7 +6089,7 @@ static inline bool compaction_ready(stru return true; /* Compaction cannot yet proceed. Do reclaim. */ - if (!compaction_suitable(zone, sc->order, sc->reclaim_idx)) + if (!compaction_suitable(zone, sc->order, sc->reclaim_idx, ALLOC_CMA)) return false; /* _ Patches currently in -mm which might be from yangge1116@126.com are mm-compaction-dont-use-alloc_cma-in-long-term-gup-flow.patch