[165/192] mm/page_alloc: reduce duration that IRQs are disabled for VM counters

Commit Message

Andrew Morton June 29, 2021, 2:41 a.m. UTC

From: Mel Gorman <[e-mail]>
Subject: mm/page_alloc: reduce duration that IRQs are disabled for VM counters

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.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Mel Gorman <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Acked-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: Chuck Lever <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jesper Dangaard Brouer <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Sebastian Andrzej Siewior <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/page_alloc.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Patch

--- a/mm/page_alloc.c~mm-page_alloc-reduce-duration-that-irqs-are-disabled-for-vm-counters
+++ a/mm/page_alloc.c
@@ -3530,11 +3530,11 @@  static struct page *rmqueue_pcplist(stru
 	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;
 }
 
@@ -3586,15 +3586,15 @@  struct page *rmqueue(struct zone *prefer
 		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 */
@@ -3607,7 +3607,7 @@  out:
 	return page;
 
 failed:
-	local_irq_restore(flags);
+	spin_unlock_irqrestore(&zone->lock, flags);
 	return NULL;
 }
 
@@ -5165,11 +5165,11 @@  unsigned long __alloc_pages_bulk(gfp_t g
 		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: