From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: [obsolete] mm-page_alloc-re-enable-softirq-use-of-per-cpu-page-allocator.patch removed from -mm tree Date: Tue, 18 Apr 2017 14:39:49 -0700 Message-ID: <58f687a5.a8S5A2jD6LICtAp5%akpm@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:38020 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752236AbdDRVju (ORCPT ); Tue, 18 Apr 2017 17:39:50 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: brouer@redhat.com, mgorman@techsingularity.net, pagupta@redhat.com, peterz@infradead.org, saeedm@mellanox.com, tariqt@mellanox.com, ttoukan.linux@gmail.com, willy@infradead.org, mm-commits@vger.kernel.org The patch titled Subject: mm, page_alloc: re-enable softirq use of per-cpu page allocator has been removed from the -mm tree. Its filename was mm-page_alloc-re-enable-softirq-use-of-per-cpu-page-allocator.patch This patch was dropped because it is obsolete ------------------------------------------------------ From: Jesper Dangaard Brouer Subject: mm, page_alloc: re-enable softirq use of per-cpu page allocator 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 will 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") Link: http://lkml.kernel.org/r/20170410150821.vcjlz7ntabtfsumm@techsingularity.net Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Mel Gorman Reported-by: Tariq Toukan Cc: Matthew Wilcox Cc: Peter Zijlstra Cc: Pankaj Gupta Cc: Tariq Toukan Cc: Saeed Mahameed Signed-off-by: Andrew Morton --- mm/page_alloc.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) diff -puN mm/page_alloc.c~mm-page_alloc-re-enable-softirq-use-of-per-cpu-page-allocator mm/page_alloc.c --- a/mm/page_alloc.c~mm-page_alloc-re-enable-softirq-use-of-per-cpu-page-allocator +++ a/mm/page_alloc.c @@ -2351,9 +2351,9 @@ static void drain_local_pages_wq(struct * 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(); } /* @@ -2488,7 +2488,11 @@ void free_hot_cold_page(struct page *pag 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; } @@ -2498,7 +2502,7 @@ void free_hot_cold_page(struct page *pag 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. @@ -2529,7 +2533,7 @@ void free_hot_cold_page(struct page *pag } out: - preempt_enable(); + local_bh_enable(); } /* @@ -2654,7 +2658,7 @@ static struct page *__rmqueue_pcplist(st { struct page *page; - VM_BUG_ON(in_interrupt()); + VM_BUG_ON(in_irq() || irqs_disabled()); do { if (list_empty(list)) { @@ -2687,7 +2691,7 @@ static struct page *rmqueue_pcplist(stru 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); @@ -2695,7 +2699,7 @@ static struct page *rmqueue_pcplist(stru __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order); zone_statistics(preferred_zone, zone); } - preempt_enable(); + local_bh_enable(); return page; } @@ -2711,7 +2715,11 @@ struct page *rmqueue(struct zone *prefer 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; _ Patches currently in -mm which might be from brouer@redhat.com are