From: Mel Gorman <mgorman@techsingularity.net>
To: Linux-MM <linux-mm@kvack.org>
Cc: Linux-RT-Users <linux-rt-users@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Chuck Lever <chuck.lever@oracle.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 6/6] mm/page_alloc: Reduce duration that IRQs are disabled for VM counters
Date: Mon, 29 Mar 2021 13:06:48 +0100 [thread overview]
Message-ID: <20210329120648.19040-7-mgorman@techsingularity.net> (raw)
In-Reply-To: <20210329120648.19040-1-mgorman@techsingularity.net>
IRQs are left disabled for the zone and node VM event counters. On some
architectures this is unnecessary and it confuses what the scope of the
locking for per-cpu lists and VM counters are.
This patch reduces the scope of IRQs being disabled via local_[lock|unlock]
and relies on preemption disabling for the per-cpu counters. This
is not completely free on all architectures as architectures
without HAVE_CMPXCHG_DOUBLE will disable/enable IRQs again for the
mod_zone_freepage_state call. However, it clarifies what the per-cpu
pages lock protects and how zone stats may need IRQs disabled if ever
called from an IRQ context.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
mm/page_alloc.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 32c64839c145..25d9351e75d8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3461,11 +3461,17 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
pcp = this_cpu_ptr(zone->per_cpu_pageset);
list = &pcp->lists[migratetype];
page = __rmqueue_pcplist(zone, migratetype, alloc_flags, pcp, list);
+ local_unlock_irqrestore(&pagesets.lock, flags);
if (page) {
+ /*
+ * per-cpu counter updates are not preempt-safe but is
+ * acceptable to race versus interrupts.
+ */
+ preempt_disable();
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1);
zone_statistics(preferred_zone, zone, 1);
+ preempt_enable();
}
- local_unlock_irqrestore(&pagesets.lock, flags);
return page;
}
@@ -3517,15 +3523,17 @@ struct page *rmqueue(struct zone *preferred_zone,
if (!page)
page = __rmqueue(zone, order, migratetype, alloc_flags);
} while (page && check_new_pages(page, order));
- spin_unlock(&zone->lock);
+ spin_unlock_irqrestore(&zone->lock, flags);
+
if (!page)
goto failed;
+
+ preempt_disable();
__mod_zone_freepage_state(zone, -(1 << order),
get_pcppage_migratetype(page));
-
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
zone_statistics(preferred_zone, zone, 1);
- local_irq_restore(flags);
+ preempt_enable();
out:
/* Separate test+clear to avoid unnecessary atomics */
@@ -5090,10 +5098,12 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
nr_populated++;
}
+ local_unlock_irqrestore(&pagesets.lock, flags);
+
+ preempt_disable();
__count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);
-
- local_unlock_irqrestore(&pagesets.lock, flags);
+ preempt_enable();
return nr_populated;
--
2.26.2
next prev parent reply other threads:[~2021-03-29 12:08 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-29 12:06 [RFC PATCH 0/6] Use local_lock for pcp protection and reduce stat overhead Mel Gorman
2021-03-29 12:06 ` [PATCH 1/6] mm/page_alloc: Split per cpu page lists and zone stats Mel Gorman
2021-03-29 12:06 ` [PATCH 2/6] mm/page_alloc: Convert per-cpu list protection to local_lock Mel Gorman
2021-03-31 9:55 ` Thomas Gleixner
2021-03-31 11:01 ` Mel Gorman
2021-03-31 17:42 ` Thomas Gleixner
2021-03-31 17:46 ` Thomas Gleixner
2021-03-31 20:42 ` Mel Gorman
2021-03-29 12:06 ` [PATCH 3/6] mm/vmstat: Convert NUMA statistics to basic NUMA counters Mel Gorman
2021-03-29 12:06 ` [PATCH 4/6] mm/vmstat: Inline NUMA event counter updates Mel Gorman
2021-03-29 12:06 ` [PATCH 5/6] mm/page_alloc: Batch the accounting updates in the bulk allocator Mel Gorman
2021-03-29 12:06 ` Mel Gorman [this message]
2021-03-30 18:51 ` [RFC PATCH 0/6] Use local_lock for pcp protection and reduce stat overhead Jesper Dangaard Brouer
2021-03-31 7:38 ` Mel Gorman
2021-03-31 8:17 ` Jesper Dangaard Brouer
2021-03-31 8:52 ` Mel Gorman
2021-03-31 9:51 ` Thomas Gleixner
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