From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.126.com (m16.mail.126.com [117.135.210.7]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DEDC82040BC; Mon, 16 Dec 2024 11:55:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734350136; cv=none; b=h/WK12NcW7U5Qopb1qwL2czI8t/L8yoxEQWn9608S4yhjnOwTwJ25/PoJP9Quka9izmvINAIROQRfAMpkqv+MEYphObDJM6LXMn3EWMBMCij0HUSU+4I7aH+TFxfSh2ldMNjGs5RBXF86b8a18YA5HuYCmdzWBH8ZF4EqBGUiB0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734350136; c=relaxed/simple; bh=kVAP8PxF3UrpxZw87ELx0B/Q/qq63lJQQJUfxtANVPU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=IFa0zVTNxBpozMYoGWOea5w1is0fAZURD8Djaz1rBPVSzytNFJ3bJkgN0nRipPAp+TWqzsG//y29cTy8i924zn11FzNsk0tVfq7r6/eclrwK42Nsi/r3FeZhcto+YJN3x0sM7gYoE2EKDiaZX+7gV4mTOqgLoDFtlAUQt1Qy6jc= 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=AKwuk2sc; arc=none smtp.client-ip=117.135.210.7 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="AKwuk2sc" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=126.com; s=s110527; h=Message-ID:Date:MIME-Version:Subject:From: Content-Type; bh=vHai0bofydY5qRIK3SpVBL5Nv8an8p0CBft58pGYi0Q=; b=AKwuk2scUnVAC4EwlrIo2GqsmFEisCsrP2hXSTmnaUv9rn7zdoI8r6V68R2p5W +6UL6qcLVL6reTSyUR0eJ2UzC1PTDvlVcv+PwYrYgVodbLQb2Bv0dtToeq+UEGPd 7YBLLMqXsDHEsgwTNZj5YVdKJDJbfAcnhXjPb4s3XDcok= Received: from [172.21.22.210] (unknown [118.242.3.34]) by gzsmtp3 (Coremail) with SMTP id pykvCgC3HlLCFGBnu946Cg--.55143S2; Mon, 16 Dec 2024 19:53:38 +0800 (CST) Message-ID: <3e160d54-5860-4616-bd32-5faff3afdb49@126.com> Date: Mon, 16 Dec 2024 19:53:38 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V4] mm, compaction: don't use ALLOC_CMA in long term GUP flow To: Baolin Wang , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, 21cnbao@gmail.com, david@redhat.com, vbabka@suse.cz, liuzixing@hygon.cn References: <1734256867-19614-1-git-send-email-yangge1116@126.com> From: Ge Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:pykvCgC3HlLCFGBnu946Cg--.55143S2 X-Coremail-Antispam: 1Uf129KBjvJXoW3GrWUuF1fur45Jr1rGw47twb_yoW3tw45pF 18Z3W2y395XFy3Cr48tF409F4Fqw4xKF18Ar1Igw1xZa4akF9293WkKFy3AF4UXryYka1Y qFWq9F9ruFsxAFJanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07Uq2NtUUUUU= X-CM-SenderInfo: 51dqwwjhrrila6rslhhfrp/1tbiOgW3G2dgFFkEhwAAsa 在 2024/12/16 16:41, Baolin Wang 写道: > > > On 2024/12/15 18:01, yangge1116@126.com wrote: >> 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 >> >> 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. >> >> Fixes: 984fdba6a32e ("mm, compaction: use proper alloc_flags in >> __compaction_suitable()") >> Cc: >> Signed-off-by: yangge >> --- >> >> V4: >> - rich the commit log description >> >> V3: >> - fix build errors >> - add ALLOC_CMA both in should_continue_reclaim() and compaction_ready() >> >> V2: >> - using the 'cc->alloc_flags' to determin if 'ALLOC_CMA' is needed >> - rich the commit log description >> >>   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(-) >> >> diff --git a/include/linux/compaction.h b/include/linux/compaction.h >> index e947764..b4c3ac3 100644 >> --- a/include/linux/compaction.h >> +++ b/include/linux/compaction.h >> @@ -90,7 +90,8 @@ extern enum compact_result >> try_to_compact_pages(gfp_t gfp_mask, >>           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_suitable(pg_data_t *pgdat) >>   } >>   static inline bool compaction_suitable(struct zone *zone, int order, >> -                              int highest_zoneidx) >> +                              int highest_zoneidx, >> +                              unsigned int alloc_flags) >>   { >>       return false; >>   } >> diff --git a/mm/compaction.c b/mm/compaction.c >> index 07bd227..585f5ab 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -2381,9 +2381,11 @@ static enum compact_result >> compact_finished(struct compact_control *cc) >>   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 >> @@ -2395,25 +2397,27 @@ 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); >> +    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); > > Why not just use 'alloc_flags & ALLOC_CMA' instead? then you can remove > the 'use_cma' variable. yes, I will change it in next version. > >>   } >>   /* >>    * 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 >> @@ -2474,7 +2478,7 @@ bool compaction_zonelist_suitable(struct >> alloc_context *ac, int order, >>           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; >>       } >> @@ -2499,7 +2503,7 @@ compaction_suit_allocation_order(struct zone >> *zone, unsigned int order, >>                     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; >> 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; > > I wonder why not pass ‘cc->alloc_flags’ as a parameter for > __isolate_free_page()? Some places that use __isolate_free_page() don't have 'cc->alloc_flags', which leads me to believe that no modification is required. I will change it in next version. > >>       } >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 5e03a61..33f5b46 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -5815,7 +5815,7 @@ static inline bool >> should_continue_reclaim(struct pglist_data *pgdat, >>                         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; >>       } >> @@ -6043,7 +6043,7 @@ static inline bool compaction_ready(struct zone >> *zone, struct scan_control *sc) >>           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; >>       /*