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From: Mel Gorman <mgorman@techsingularity.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Chuck Lever <chuck.lever@oracle.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Michal Hocko <mhocko@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>, Linux-MM <linux-mm@kvack.org>,
	Linux-RT-Users <linux-rt-users@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 6/9] mm/page_alloc: Reduce duration that IRQs are disabled for VM counters
Date: Wed, 12 May 2021 10:54:55 +0100	[thread overview]
Message-ID: <20210512095458.30632-7-mgorman@techsingularity.net> (raw)
In-Reply-To: <20210512095458.30632-1-mgorman@techsingularity.net>

IRQs are left disabled for the zone and node VM event counters. This is
unnecessary as the affected counters are allowed to race for preemmption
and IRQs.

This patch reduces the scope of IRQs being disabled
via local_[lock|unlock]_irq on !PREEMPT_RT kernels. One
__mod_zone_freepage_state is still called with IRQs disabled. While this
could be moved out, it's not free on all architectures as some require
IRQs to be disabled for mod_zone_page_state on !PREEMPT_RT kernels.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/page_alloc.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7970efa142b0..5879b595b74b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3519,11 +3519,11 @@ 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) {
 		__count_zid_vm_events(PGALLOC, page_zonenum(page), 1);
 		zone_statistics(preferred_zone, zone, 1);
 	}
-	local_unlock_irqrestore(&pagesets.lock, flags);
 	return page;
 }
 
@@ -3575,15 +3575,15 @@ 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);
 	if (!page)
 		goto failed;
+
 	__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);
-	local_irq_restore(flags);
 
 out:
 	/* Separate test+clear to avoid unnecessary atomics */
@@ -3596,7 +3596,7 @@ struct page *rmqueue(struct zone *preferred_zone,
 	return page;
 
 failed:
-	local_irq_restore(flags);
+	spin_unlock_irqrestore(&zone->lock, flags);
 	return NULL;
 }
 
@@ -5147,11 +5147,11 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 		nr_populated++;
 	}
 
+	local_unlock_irqrestore(&pagesets.lock, flags);
+
 	__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);
-
 	return nr_populated;
 
 failed_irq:
-- 
2.26.2


  parent reply	other threads:[~2021-05-12  9:56 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-12  9:54 [PATCH 0/9 v6] Use local_lock for pcp protection and reduce stat overhead Mel Gorman
2021-05-12  9:54 ` [PATCH 1/9] mm/page_alloc: Split per cpu page lists and zone stats Mel Gorman
2021-05-12  9:54 ` [PATCH 2/9] mm/page_alloc: Convert per-cpu list protection to local_lock Mel Gorman
2021-05-12  9:54 ` [PATCH 3/9] mm/vmstat: Convert NUMA statistics to basic NUMA counters Mel Gorman
2021-05-12 10:11   ` Vlastimil Babka
2021-05-12  9:54 ` [PATCH 4/9] mm/vmstat: Inline NUMA event counter updates Mel Gorman
2021-05-12  9:54 ` [PATCH 5/9] mm/page_alloc: Batch the accounting updates in the bulk allocator Mel Gorman
2021-05-12  9:54 ` Mel Gorman [this message]
2021-05-12  9:54 ` [PATCH 7/9] mm/page_alloc: Explicitly acquire the zone lock in __free_pages_ok Mel Gorman
2021-05-12  9:54 ` [PATCH 8/9] mm/page_alloc: Avoid conflating IRQs disabled with zone->lock Mel Gorman
2021-05-12  9:54 ` [PATCH 9/9] mm/page_alloc: Update PGFREE outside the zone lock in __free_pages_ok Mel Gorman
2021-05-12 13:06 ` [PATCH 0/9 v6] Use local_lock for pcp protection and reduce stat overhead Peter Zijlstra
  -- strict thread matches above, loose matches on Subject: below --
2021-04-22 11:14 [PATCH 0/9 v5] " Mel Gorman
2021-04-22 11:14 ` [PATCH 6/9] mm/page_alloc: Reduce duration that IRQs are disabled for VM counters Mel Gorman

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