From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.126.com (m16.mail.126.com [117.135.210.6]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3A9E829A1 for ; Thu, 16 Jan 2025 01:34:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.6 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736991255; cv=none; b=rY+1yWy9k5cx4MkZ8zIEwdQLBnMASklSYzQU1tARceaaUkB6eyVp7Gcuc+TjCLL3BZ0DN5ehL7WM4OOorO6rLKkNlanX5N76aFM5dxwuOPe1up170klxjJVb3i7K8R4/6+BhiVtUftFJAo/Fo39T9Vm72mG5ohA35mZPFJdHjLA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736991255; c=relaxed/simple; bh=D+mXEm4QA8WBGEQofZ3UrjBbK/+ERWvoOAhQyXCoEt4=; h=From:To:Cc:Subject:Date:Message-Id; b=F023azqEzL9MyN/vN3Gb/TAt6Ke7eDmk5j1/dwtQ+ctbAFcQOkSSOne2LawA7iQtY1HblJjsSNTWp0wrqLbrNpPjODG/FEoSUTAl7vAGuT8G5dmUtMXG/04dm6nuLg4ExQ8ea9237EjV7ucZcvA6Ts2of/QqFAl/8s+C99ZfmCA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=126.com; spf=pass smtp.mailfrom=126.com; dkim=pass (1024-bit key) header.d=126.com header.i=@126.com header.b=TBsggUsP; arc=none smtp.client-ip=117.135.210.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=126.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=126.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=126.com header.i=@126.com header.b="TBsggUsP" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=126.com; s=s110527; h=From:Subject:Date:Message-Id; bh=QuZuiBxQN68/BS2asW Bdr7x38VeHNcrbO5vLMPnuC6o=; b=TBsggUsP0XJkaORvmMjC3dV3tCWxyhjKJm xvt8+pkjI9c5+8VIzeJuem+j4mhj7hEBo8I4ep9I2akeFkTtDIQwt/xsdLBVFQFi 3xX3/cm+Hh/b6oM/a246xQSiXQkEiYIrB+Ejo4K/9nE0wmkm4o0TPjaedgXZV+6i PNYQPTMeE= Received: from hg-OptiPlex-7040.hygon.cn (unknown []) by gzga-smtp-mtada-g0-1 (Coremail) with SMTP id _____wD3z83vYYhnxsb+BA--.20958S2; Thu, 16 Jan 2025 09:33:35 +0800 (CST) From: yangge1116@126.com To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, 21cnbao@gmail.com, david@redhat.com, baolin.wang@linux.alibaba.com, hannes@cmpxchg.org, vbabka@suse.cz, liuzixing@hygon.cn, yangge Subject: [PATCH V2] mm: compaction: use the actual allocation context to determine the watermarks for costly order during async memory compaction Date: Thu, 16 Jan 2025 09:33:34 +0800 Message-Id: <1736991214-29069-1-git-send-email-yangge1116@126.com> X-Mailer: git-send-email 2.7.4 X-CM-TRANSID:_____wD3z83vYYhnxsb+BA--.20958S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxZrW3CFyxAFy5Cr13Kr1DGFg_yoWrtw45pa 18ur13C395XF43CF4xta1kuF1Ygw4xJF1UJF1Ivw1UZw4akFn2v3WDta45AF4UXry3JFWj vFZ09F1DCanxAaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0zRYhFxUUUUU= X-CM-SenderInfo: 51dqwwjhrrila6rslhhfrp/1tbifh7WG2eIVpHBHQABsY Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: From: yangge 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. 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. There is 16GB of free CMA memory on a NUMA node, which is sufficient to pass the order-0 watermark check, causing the __compaction_suitable() function to consistently return true. For costly allocations, if the __compaction_suitable() function always returns true, it causes the __alloc_pages_slowpath() function to fail to exit at the appropriate point. This prevents timely fallback to allocating memory on other nodes, ultimately 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 We could use the real unmovable allocation context to have __zone_watermark_unusable_free() subtract CMA pages, and thus we won't pass the order-0 check anymore once the non-CMA part is exhausted. There is some risk that in some different scenario the compaction could in fact migrate pages from the exhausted non-CMA part of the zone to the CMA part and succeed, and we'll skip it instead. But only __GFP_NORETRY allocations should be affected in the immediate "goto nopage" when compaction is skipped, others will attempt with DEF_COMPACT_PRIORITY anyway and won't fail without trying to compact-migrate the non-CMA pageblocks into CMA pageblocks first, so it should be fine. After this fix, it only takes a few tens of seconds to start a 32GB virtual machine with device passthrough functionality. Link: https://lore.kernel.org/lkml/1736335854-548-1-git-send-email-yangge1116@126.com/ Signed-off-by: yangge Acked-by: Vlastimil Babka --- V2: - update code and message suggested by Vlastimil mm/compaction.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 07bd227..3de7b67 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -2490,7 +2490,8 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order, */ static enum compact_result compaction_suit_allocation_order(struct zone *zone, unsigned int order, - int highest_zoneidx, unsigned int alloc_flags) + int highest_zoneidx, unsigned int alloc_flags, + bool async) { unsigned long watermark; @@ -2499,6 +2500,23 @@ compaction_suit_allocation_order(struct zone *zone, unsigned int order, alloc_flags)) return COMPACT_SUCCESS; + /* + * For unmovable allocations (without ALLOC_CMA), check if there is enough + * free memory in the non-CMA pageblocks. Otherwise compaction could form + * the high-order page in CMA pageblocks, which would not help the + * allocation to succeed. However, limit the check to costly order async + * compaction (such as opportunistic THP attempts) because there is the + * possibility that compaction would migrate pages from non-CMA to CMA + * pageblock. + */ + if (order > PAGE_ALLOC_COSTLY_ORDER && async && + !(alloc_flags & ALLOC_CMA)) { + watermark = low_wmark_pages(zone) + compact_gap(order); + if (!__zone_watermark_ok(zone, 0, watermark, highest_zoneidx, + 0, zone_page_state(zone, NR_FREE_PAGES))) + return COMPACT_SKIPPED; + } + if (!compaction_suitable(zone, order, highest_zoneidx)) return COMPACT_SKIPPED; @@ -2534,7 +2552,8 @@ compact_zone(struct compact_control *cc, struct capture_control *capc) if (!is_via_compact_memory(cc->order)) { ret = compaction_suit_allocation_order(cc->zone, cc->order, cc->highest_zoneidx, - cc->alloc_flags); + cc->alloc_flags, + cc->mode == MIGRATE_ASYNC); if (ret != COMPACT_CONTINUE) return ret; } @@ -3037,7 +3056,8 @@ static bool kcompactd_node_suitable(pg_data_t *pgdat) ret = compaction_suit_allocation_order(zone, pgdat->kcompactd_max_order, - highest_zoneidx, ALLOC_WMARK_MIN); + highest_zoneidx, ALLOC_WMARK_MIN, + false); if (ret == COMPACT_CONTINUE) return true; } @@ -3078,7 +3098,8 @@ static void kcompactd_do_work(pg_data_t *pgdat) continue; ret = compaction_suit_allocation_order(zone, - cc.order, zoneid, ALLOC_WMARK_MIN); + cc.order, zoneid, ALLOC_WMARK_MIN, + false); if (ret != COMPACT_CONTINUE) continue; -- 2.7.4