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Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH] mm/page_alloc: call check_new_pages() while zone spinlock is not held Content-Language: en-US To: Eric Dumazet , Eric Dumazet Cc: Andrew Morton , linux-kernel , linux-mm , Mel Gorman , Michal Hocko , Shakeel Butt , Wei Xu , Greg Thelen , Hugh Dickins , David Rientjes References: <20220304015941.1704249-1-eric.dumazet@gmail.com> From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 24BF51A000F X-Stat-Signature: mr3omipa37p786gku6eeg1wob5drn69t Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=wJt+IL30; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=ZP5UB2fC; spf=pass (imf19.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1646382753-860675 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: On 3/4/22 03:09, Eric Dumazet wrote: > On Thu, Mar 3, 2022 at 5:59 PM Eric Dumazet wrote: >> >> From: Eric Dumazet >> >> For high order pages not using pcp, rmqueue() is currently calling >> the costly check_new_pages() while zone spinlock is held. >> >> This is not needed, we can release the spinlock sooner to reduce >> zone spinlock contention. >> >> Signed-off-by: Eric Dumazet >> Cc: Mel Gorman >> Cc: Vlastimil Babka >> Cc: Michal Hocko >> Cc: Shakeel Butt >> Cc: Wei Xu >> Cc: Greg Thelen >> Cc: Hugh Dickins >> Cc: David Rientjes >> --- >> mm/page_alloc.c | 17 +++++++---------- >> 1 file changed, 7 insertions(+), 10 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 3589febc6d31928f850ebe5a4015ddc40e0469f3..0890a65f8cc2259e82bc1f5ba95a592fb30f9fb8 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -3685,7 +3685,6 @@ struct page *rmqueue(struct zone *preferred_zone, >> gfp_t gfp_flags, unsigned int alloc_flags, >> int migratetype) >> { >> - unsigned long flags; >> struct page *page; >> >> if (likely(pcp_allowed_order(order))) { >> @@ -3706,10 +3705,12 @@ struct page *rmqueue(struct zone *preferred_zone, >> * allocate greater than order-1 page units with __GFP_NOFAIL. >> */ >> WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1)); >> - spin_lock_irqsave(&zone->lock, flags); >> >> do { >> + unsigned long flags; >> + >> page = NULL; >> + spin_lock_irqsave(&zone->lock, flags); >> /* >> * order-0 request can reach here when the pcplist is skipped >> * due to non-CMA allocation context. HIGHATOMIC area is >> @@ -3723,13 +3724,13 @@ struct page *rmqueue(struct zone *preferred_zone, >> } >> if (!page) >> page = __rmqueue(zone, order, migratetype, alloc_flags); >> - } while (page && check_new_pages(page, order)); >> - if (!page) >> - goto failed; >> + spin_unlock_irqrestore(&zone->lock, flags); >> + if (!page) >> + return NULL; >> + } while (check_new_pages(page, order)); >> > > Oh well, it seems hard irqs have to be disabled when calling the > following function. Ah, you found out already. Well maybe it could simply be moved inside the loop under the locked section and always done when page != NULL? I mean if check_new_pages() fails we just leak the problematic pages anyway so they are no longer free to allocate anymore and we should not count them as such. > I will send a V2. > >> __mod_zone_freepage_state(zone, -(1 << order), >> get_pcppage_migratetype(page)); >> - spin_unlock_irqrestore(&zone->lock, flags); >> >> __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order); >> zone_statistics(preferred_zone, zone, 1); >> @@ -3743,10 +3744,6 @@ struct page *rmqueue(struct zone *preferred_zone, >> >> VM_BUG_ON_PAGE(page && bad_range(zone, page), page); >> return page; >> - >> -failed: >> - spin_unlock_irqrestore(&zone->lock, flags); >> - return NULL; >> } >> >> #ifdef CONFIG_FAIL_PAGE_ALLOC >> -- >> 2.35.1.616.g0bdcbb4464-goog >>