From patchwork Wed May 12 09:54:51 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mel Gorman X-Patchwork-Id: 436018 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58AD7C433ED for ; Wed, 12 May 2021 09:55:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 266FE613F3 for ; Wed, 12 May 2021 09:55:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230338AbhELJ4k (ORCPT ); Wed, 12 May 2021 05:56:40 -0400 Received: from outbound-smtp30.blacknight.com ([81.17.249.61]:43651 "EHLO outbound-smtp30.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230343AbhELJ4j (ORCPT ); Wed, 12 May 2021 05:56:39 -0400 Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp30.blacknight.com (Postfix) with ESMTPS id D0EA6BAB09 for ; Wed, 12 May 2021 10:55:30 +0100 (IST) Received: (qmail 26996 invoked from network); 12 May 2021 09:55:30 -0000 Received: from unknown (HELO stampy.112glenside.lan) (mgorman@techsingularity.net@[84.203.23.168]) by 81.17.254.9 with ESMTPA; 12 May 2021 09:55:30 -0000 From: Mel Gorman To: Andrew Morton Cc: Chuck Lever , Jesper Dangaard Brouer , Thomas Gleixner , Sebastian Andrzej Siewior , Peter Zijlstra , Ingo Molnar , Michal Hocko , Vlastimil Babka , Linux-MM , Linux-RT-Users , LKML , Mel Gorman Subject: [PATCH 2/9] mm/page_alloc: Convert per-cpu list protection to local_lock Date: Wed, 12 May 2021 10:54:51 +0100 Message-Id: <20210512095458.30632-3-mgorman@techsingularity.net> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210512095458.30632-1-mgorman@techsingularity.net> References: <20210512095458.30632-1-mgorman@techsingularity.net> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org There is a lack of clarity of what exactly local_irq_save/local_irq_restore protects in page_alloc.c . It conflates the protection of per-cpu page allocation structures with per-cpu vmstat deltas. This patch protects the PCP structure using local_lock which for most configurations is identical to IRQ enabling/disabling. The scope of the lock is still wider than it should be but this is decreased later. It is possible for the local_lock to be embedded safely within struct per_cpu_pages but it adds complexity to free_unref_page_list. [lkp@intel.com: Make pagesets static] Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka --- include/linux/mmzone.h | 2 ++ mm/page_alloc.c | 50 +++++++++++++++++++++++++++++------------- 2 files changed, 37 insertions(+), 15 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index a8cd4881faf2..30a1b5edbe90 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -20,6 +20,7 @@ #include #include #include +#include #include /* Free memory management - zoned buddy allocator. */ @@ -337,6 +338,7 @@ enum zone_watermarks { #define high_wmark_pages(z) (z->_watermark[WMARK_HIGH] + z->watermark_boost) #define wmark_pages(z, i) (z->_watermark[i] + z->watermark_boost) +/* Fields and list protected by pagesets local_lock in page_alloc.c */ struct per_cpu_pages { int count; /* number of pages in the list */ int high; /* high watermark, emptying needed */ diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f447b691b4eb..beca5ab7ddf3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -122,6 +122,13 @@ typedef int __bitwise fpi_t; static DEFINE_MUTEX(pcp_batch_high_lock); #define MIN_PERCPU_PAGELIST_FRACTION (8) +struct pagesets { + local_lock_t lock; +}; +static DEFINE_PER_CPU(struct pagesets, pagesets) = { + .lock = INIT_LOCAL_LOCK(lock), +}; + #ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID DEFINE_PER_CPU(int, numa_node); EXPORT_PER_CPU_SYMBOL(numa_node); @@ -1453,6 +1460,10 @@ static void free_pcppages_bulk(struct zone *zone, int count, } while (--count && --batch_free && !list_empty(list)); } + /* + * local_lock_irq held so equivalent to spin_lock_irqsave for + * both PREEMPT_RT and non-PREEMPT_RT configurations. + */ spin_lock(&zone->lock); isolated_pageblocks = has_isolate_pageblock(zone); @@ -1573,6 +1584,11 @@ static void __free_pages_ok(struct page *page, unsigned int order, return; migratetype = get_pfnblock_migratetype(page, pfn); + + /* + * TODO FIX: Disable IRQs before acquiring IRQ-safe zone->lock + * and protect vmstat updates. + */ local_irq_save(flags); __count_vm_events(PGFREE, 1 << order); free_one_page(page_zone(page), page, pfn, order, migratetype, @@ -2955,6 +2971,10 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order, { int i, allocated = 0; + /* + * local_lock_irq held so equivalent to spin_lock_irqsave for + * both PREEMPT_RT and non-PREEMPT_RT configurations. + */ spin_lock(&zone->lock); for (i = 0; i < count; ++i) { struct page *page = __rmqueue(zone, order, migratetype, @@ -3007,12 +3027,12 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp) unsigned long flags; int to_drain, batch; - local_irq_save(flags); + local_lock_irqsave(&pagesets.lock, flags); batch = READ_ONCE(pcp->batch); to_drain = min(pcp->count, batch); if (to_drain > 0) free_pcppages_bulk(zone, to_drain, pcp); - local_irq_restore(flags); + local_unlock_irqrestore(&pagesets.lock, flags); } #endif @@ -3028,13 +3048,13 @@ static void drain_pages_zone(unsigned int cpu, struct zone *zone) unsigned long flags; struct per_cpu_pages *pcp; - local_irq_save(flags); + local_lock_irqsave(&pagesets.lock, flags); pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu); if (pcp->count) free_pcppages_bulk(zone, pcp->count, pcp); - local_irq_restore(flags); + local_unlock_irqrestore(&pagesets.lock, flags); } /* @@ -3297,9 +3317,9 @@ void free_unref_page(struct page *page) if (!free_unref_page_prepare(page, pfn)) return; - local_irq_save(flags); + local_lock_irqsave(&pagesets.lock, flags); free_unref_page_commit(page, pfn); - local_irq_restore(flags); + local_unlock_irqrestore(&pagesets.lock, flags); } /* @@ -3319,7 +3339,7 @@ void free_unref_page_list(struct list_head *list) set_page_private(page, pfn); } - local_irq_save(flags); + local_lock_irqsave(&pagesets.lock, flags); list_for_each_entry_safe(page, next, list, lru) { unsigned long pfn = page_private(page); @@ -3332,12 +3352,12 @@ void free_unref_page_list(struct list_head *list) * a large list of pages to free. */ if (++batch_count == SWAP_CLUSTER_MAX) { - local_irq_restore(flags); + local_unlock_irqrestore(&pagesets.lock, flags); batch_count = 0; - local_irq_save(flags); + local_lock_irqsave(&pagesets.lock, flags); } } - local_irq_restore(flags); + local_unlock_irqrestore(&pagesets.lock, flags); } /* @@ -3494,7 +3514,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, struct page *page; unsigned long flags; - local_irq_save(flags); + local_lock_irqsave(&pagesets.lock, flags); pcp = this_cpu_ptr(zone->per_cpu_pageset); list = &pcp->lists[migratetype]; page = __rmqueue_pcplist(zone, migratetype, alloc_flags, pcp, list); @@ -3502,7 +3522,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone, __count_zid_vm_events(PGALLOC, page_zonenum(page), 1); zone_statistics(preferred_zone, zone); } - local_irq_restore(flags); + local_unlock_irqrestore(&pagesets.lock, flags); return page; } @@ -5096,7 +5116,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, goto failed; /* Attempt the batch allocation */ - local_irq_save(flags); + local_lock_irqsave(&pagesets.lock, flags); pcp = this_cpu_ptr(zone->per_cpu_pageset); pcp_list = &pcp->lists[ac.migratetype]; @@ -5134,12 +5154,12 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, nr_populated++; } - local_irq_restore(flags); + local_unlock_irqrestore(&pagesets.lock, flags); return nr_populated; failed_irq: - local_irq_restore(flags); + local_unlock_irqrestore(&pagesets.lock, flags); failed: page = __alloc_pages(gfp, 0, preferred_nid, nodemask);