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Commit cabe76e9 authored by Vinayak Menon's avatar Vinayak Menon
Browse files

mm: page-writeback: fix page state calculation in throttle_vm_writeout 



It was found that a number of tasks were blocked in the reclaim path
(throttle_vm_writeout) for seconds, because of vmstat_diff not being
synced in time. Fix that by adding a new function
global_page_state_snapshot.

Signed-off-by: default avatarVinayak Menon <vinmenon@codeaurora.org>
Change-Id: Iec167635ad724a55c27bdbd49eb8686e7857216c
parent 21015dfb

include/linux/vmstat.h

+20 −0
Original line number Diff line number Diff line
@@ -160,6 +160,26 @@ static inline unsigned long zone_page_state_snapshot(struct zone *zone, 
	return x;

}



static inline unsigned long global_page_state_snapshot(enum zone_stat_item item)

{

	long x = atomic_long_read(&vm_stat[item]);



#ifdef CONFIG_SMP

	struct zone *zone;

	int cpu;



	for_each_online_cpu(cpu) {

		for_each_populated_zone(zone)

			x += per_cpu_ptr(zone->pageset,

				cpu)->vm_stat_diff[item];

	}



	if (x < 0)

		x = 0;

#endif

	return x;

}



#ifdef CONFIG_NUMA

/*

 * Determine the per node value of a stat item. This function

mm/page-writeback.c

+6 −0
Original line number Diff line number Diff line
@@ -1639,6 +1639,12 @@ void throttle_vm_writeout(gfp_t gfp_mask) 
                if (global_page_state(NR_UNSTABLE_NFS) +

			global_page_state(NR_WRITEBACK) <= dirty_thresh)

                        	break;

		/* Try safe version */

		else if (unlikely(global_page_state_snapshot(NR_UNSTABLE_NFS) +

			global_page_state_snapshot(NR_WRITEBACK) <=

				dirty_thresh))

				break;



                congestion_wait(BLK_RW_ASYNC, HZ/10);



		/*