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Fri, 13 Dec 2024 15:37:18 +0800 (CST) From: yangge1116@126.com To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, 21cnbao@gmail.com, david@redhat.com, baolin.wang@linux.alibaba.com, vbabka@suse.cz, liuzixing@hygon.cn, yangge Subject: [PATCH] mm, compaction: don't use ALLOC_CMA in long term GUP flow Date: Fri, 13 Dec 2024 15:37:12 +0800 Message-Id: <1734075432-14131-1-git-send-email-yangge1116@126.com> X-Mailer: git-send-email 2.7.4 X-CM-TRANSID: _____wDHz7wu5FtnmTDGAA--.2052S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxXF4xCw1rXr1fXr4UCF17ZFb_yoWrXr1DpF 4xA3WDAws8XFyYkr4kJw4v9F4Ykw4xGF45Gr92gw18uw1akFySv3Z7KFy7AFW5WryYya1Y qFWq93srAF43AaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0zNLvKwUUUUU= X-Originating-IP: [118.242.3.34] X-CM-SenderInfo: 51dqwwjhrrila6rslhhfrp/1tbiOge0G2db06TqnwAAss X-Rspamd-Queue-Id: DCE73120016 X-Rspamd-Server: rspam12 X-Stat-Signature: wkj5mighmmost6j9p4gtwka1zg4uybkp X-Rspam-User: X-HE-Tag: 1734075413-294672 X-HE-Meta: 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 ccw8MPvk zf33bUufuNZBdwilFKNU/L9ZNp9JxVBR17YGblMGQ86lJlbjTVY4M09NvP1clA2mcaJi9X9JSWm6HaWiHex+wfd46ObRL5pWhDVgulAk/5qWhq6M+gDgZ4vyxHWYsS1XRywm6NElsmbCy8lSSbvmboAhGuXR9RnG+vdIxcGmrJUyXLlUrtVPaSZf3lSycvCZ1iJr0eVHhGlcHfI314bybt7DOg4AYh9IZxqyLp0y4oMrb5h1iXb0t7Vkw+EUQlid25o9LzXX4mmJLBbeEXvskux9KTAxml1ZmbT6RpUdU7wbxYfGlQbGqiREnayMIkf9yOnpUFCTNOjgCHbpwC8/HRBXM+w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: yangge 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 To sum up, during long term GUP flow, we should remove ALLOC_CMA both in __compaction_suitable() and __isolate_free_page(). Fixes: 984fdba6a32e ("mm, compaction: use proper alloc_flags in __compaction_suitable()") Cc: Signed-off-by: yangge --- mm/compaction.c | 8 +++++--- mm/page_alloc.c | 4 +++- 2 files changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 07bd227..044c2247 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -2384,6 +2384,7 @@ static bool __compaction_suitable(struct zone *zone, int order, unsigned long wmark_target) { unsigned long watermark; + bool pin; /* * Watermarks for order-0 must be met for compaction to be able to * isolate free pages for migration targets. This means that the @@ -2395,14 +2396,15 @@ static bool __compaction_suitable(struct zone *zone, int order, * 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); + pin = !!(current->flags & PF_MEMALLOC_PIN); return __zone_watermark_ok(zone, 0, watermark, highest_zoneidx, - ALLOC_CMA, wmark_target); + pin ? 0 : ALLOC_CMA, wmark_target); } /* diff --git a/mm/page_alloc.c b/mm/page_alloc.c index dde19db..9a5dfda 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2813,6 +2813,7 @@ int __isolate_free_page(struct page *page, unsigned int order) { struct zone *zone = page_zone(page); int mt = get_pageblock_migratetype(page); + bool pin; if (!is_migrate_isolate(mt)) { unsigned long watermark; @@ -2823,7 +2824,8 @@ int __isolate_free_page(struct page *page, unsigned int order) * 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; }