Hello Vinayak,
On Wed, Jan 25, 2017 at 05:08:38PM +0530, Vinayak Menon wrote:
> It is noticed that during a global reclaim the memory
> reclaimed via shrinking the slabs can sometimes result
> in reclaimed pages being greater than the scanned pages
> in shrink_node. When this is passed to vmpressure, the
I don't know you are saying zsmalloc. Anyway, it's one of those which
free larger pages than requested. I should fix that but was not sent
yet, unfortunately.
> unsigned arithmetic results in the pressure value to be
> huge, thus resulting in a critical event being sent to
> root cgroup. Fix this by not passing the reclaimed slab
> count to vmpressure, with the assumption that vmpressure
> should show the actual pressure on LRU which is now
> diluted by adding reclaimed slab without a corresponding
> scanned value.
I can't guess justfication of your assumption from the description.
Why do we consider only LRU pages for vmpressure? Could you elaborate
a bit?
Thanks.
>
> Signed-off-by: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx>
> ---
> mm/vmscan.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 947ab6f..37c4486 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2594,16 +2594,16 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
> sc->nr_scanned - nr_scanned,
> node_lru_pages);
>
> - if (reclaim_state) {
> - sc->nr_reclaimed += reclaim_state->reclaimed_slab;
> - reclaim_state->reclaimed_slab = 0;
> - }
> -
> /* Record the subtree's reclaim efficiency */
> vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
> sc->nr_scanned - nr_scanned,
> sc->nr_reclaimed - nr_reclaimed);
>
> + if (reclaim_state) {
> + sc->nr_reclaimed += reclaim_state->reclaimed_slab;
> + reclaim_state->reclaimed_slab = 0;
> + }
> +
> if (sc->nr_reclaimed - nr_reclaimed)
> reclaimable = true;
>
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