From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753787AbdDJPIs (ORCPT ); Mon, 10 Apr 2017 11:08:48 -0400 Received: from outbound-smtp06.blacknight.com ([81.17.249.39]:36139 "EHLO outbound-smtp06.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751812AbdDJPIY (ORCPT ); Mon, 10 Apr 2017 11:08:24 -0400 Date: Mon, 10 Apr 2017 16:08:21 +0100 From: Mel Gorman To: akpm@linux-foundation.org Cc: brouer@redhat.com, willy@infradead.org, peterz@infradead.org, pagupta@redhat.com, ttoukan.linux@gmail.com, tariqt@mellanox.com, netdev@vger.kernel.org, saeedm@mellanox.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] mm, page_alloc: re-enable softirq use of per-cpu page allocator Message-ID: <20170410150821.vcjlz7ntabtfsumm@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline User-Agent: Mutt/1.6.2 (2016-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jesper Dangaard Brouer IRQ context were excluded from using the Per-Cpu-Pages (PCP) lists caching of order-0 pages in commit 374ad05ab64d ("mm, page_alloc: only use per-cpu allocator for irq-safe requests"). This unfortunately also included excluded SoftIRQ. This hurt the performance for the use-case of refilling DMA RX rings in softirq context. This patch re-allow softirq context, which should be safe by disabling BH/softirq, while accessing the list. PCP-lists access from both hard-IRQ and NMI context must not be allowed. Peter Zijlstra says in_nmi() code never access the page allocator, thus it should be sufficient to only test for !in_irq(). One concern with this change is adding a BH (enable) scheduling point at both PCP alloc and free. If further concerns are highlighted by this patch, the result wiill be to revert 374ad05ab64d and try again at a later date to offset the irq enable/disable overhead. Fixes: 374ad05ab64d ("mm, page_alloc: only use per-cpu allocator for irq-safe requests") Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Mel Gorman --- mm/page_alloc.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6cbde310abed..d7e986967910 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2351,9 +2351,9 @@ static void drain_local_pages_wq(struct work_struct *work) * cpu which is allright but we also have to make sure to not move to * a different one. */ - preempt_disable(); + local_bh_disable(); drain_local_pages(NULL); - preempt_enable(); + local_bh_enable(); } /* @@ -2481,7 +2481,11 @@ void free_hot_cold_page(struct page *page, bool cold) unsigned long pfn = page_to_pfn(page); int migratetype; - if (in_interrupt()) { + /* + * Exclude (hard) IRQ and NMI context from using the pcplists. + * But allow softirq context, via disabling BH. + */ + if (in_irq() || irqs_disabled()) { __free_pages_ok(page, 0); return; } @@ -2491,7 +2495,7 @@ void free_hot_cold_page(struct page *page, bool cold) migratetype = get_pfnblock_migratetype(page, pfn); set_pcppage_migratetype(page, migratetype); - preempt_disable(); + local_bh_disable(); /* * We only track unmovable, reclaimable and movable on pcp lists. @@ -2522,7 +2526,7 @@ void free_hot_cold_page(struct page *page, bool cold) } out: - preempt_enable(); + local_bh_enable(); } /* @@ -2647,7 +2651,7 @@ static struct page *__rmqueue_pcplist(struct zone *zone, int migratetype, { struct page *page; - VM_BUG_ON(in_interrupt()); + VM_BUG_ON(in_irq() || irqs_disabled()); do { if (list_empty(list)) { @@ -2680,7 +2684,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, bool cold = ((gfp_flags & __GFP_COLD) != 0); struct page *page; - preempt_disable(); + local_bh_disable(); pcp = &this_cpu_ptr(zone->pageset)->pcp; list = &pcp->lists[migratetype]; page = __rmqueue_pcplist(zone, migratetype, cold, pcp, list); @@ -2688,7 +2692,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order); zone_statistics(preferred_zone, zone); } - preempt_enable(); + local_bh_enable(); return page; } @@ -2704,7 +2708,11 @@ struct page *rmqueue(struct zone *preferred_zone, unsigned long flags; struct page *page; - if (likely(order == 0) && !in_interrupt()) { + /* + * Exclude (hard) IRQ and NMI context from using the pcplists. + * But allow softirq context, via disabling BH. + */ + if (likely(order == 0) && !(in_irq() || irqs_disabled()) ) { page = rmqueue_pcplist(preferred_zone, zone, order, gfp_flags, migratetype); goto out;