On Tue, 26 Apr 2011 08:36:54 +0100 Mel Gorman <mgorman@xxxxxxx> wrote:
> Under significant pressure when writing back to network-backed storage,
> direct reclaimers may get throttled. This is expected to be a
> short-lived event and the processes get woken up again but processes do
> get stalled. This patch counts how many times such stalling occurs. It's
> up to the administrator whether to reduce these stalls by increasing
> min_free_kbytes.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> ---
> include/linux/vm_event_item.h | 1 +
> mm/vmscan.c | 1 +
> mm/vmstat.c | 1 +
> 3 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> index 03b90cdc..652e5f3 100644
> --- a/include/linux/vm_event_item.h
> +++ b/include/linux/vm_event_item.h
> @@ -29,6 +29,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
> FOR_ALL_ZONES(PGSTEAL),
> FOR_ALL_ZONES(PGSCAN_KSWAPD),
> FOR_ALL_ZONES(PGSCAN_DIRECT),
> + PGSCAN_DIRECT_THROTTLE,
> #ifdef CONFIG_NUMA
> PGSCAN_ZONE_RECLAIM_FAILED,
> #endif
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 8b6da2b..e88138b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2154,6 +2154,7 @@ static void throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
> goto out;
>
> /* Throttle */
> + count_vm_event(PGSCAN_DIRECT_THROTTLE);
> do {
> schedule();
> finish_wait(&zone->zone_pgdat->pfmemalloc_wait, &wait);
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index a2b7344..5725387 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -911,6 +911,7 @@ const char * const vmstat_text[] = {
> TEXTS_FOR_ZONES("pgsteal")
> TEXTS_FOR_ZONES("pgscan_kswapd")
> TEXTS_FOR_ZONES("pgscan_direct")
> + "pgscan_direct_throttle",
>
> #ifdef CONFIG_NUMA
> "zone_reclaim_failed",
I like this approach. Make the information available, but don't make a fuss
about it.
Actually, I like the whole series - I'm really having to dig deep to find
anything to complain about :-)
Feel free to put
Reviewed-by: NeilBrown <neilb@xxxxxxx>
against anything that I haven't commented on.
Thanks,
NeilBrown
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