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SubjectRe: [patch 03/11] mm: vmscan: distinguish between memcg triggering reclaim and memcg being scanned
On Mon 12-09-11 12:57:20, Johannes Weiner wrote:
> Memory cgroup hierarchies are currently handled completely outside of
> the traditional reclaim code, which is invoked with a single memory
> cgroup as an argument for the whole call stack.
>
> Subsequent patches will switch this code to do hierarchical reclaim,
> so there needs to be a distinction between a) the memory cgroup that
> is triggering reclaim due to hitting its limit and b) the memory
> cgroup that is being scanned as a child of a).
>
> This patch introduces a struct mem_cgroup_zone that contains the
> combination of the memory cgroup and the zone being scanned, which is
> then passed down the stack instead of the zone argument.
>
> Signed-off-by: Johannes Weiner <jweiner@redhat.com>

Looks good to me. Some minor comments bellow
Anyways:
Reviewed-by: Michal Hocko <mhocko@suse.cz>

> ---
> mm/vmscan.c | 251 +++++++++++++++++++++++++++++++++--------------------------
> 1 files changed, 142 insertions(+), 109 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 354f125..92f4e22 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
[...]
> @@ -1853,13 +1865,13 @@ static int vmscan_swappiness(struct scan_control *sc)
> *
> * nr[0] = anon pages to scan; nr[1] = file pages to scan
> */
> -static void get_scan_count(struct zone *zone, struct scan_control *sc,
> - unsigned long *nr, int priority)
> +static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
> + unsigned long *nr, int priority)
> {
> unsigned long anon, file, free;
> unsigned long anon_prio, file_prio;
> unsigned long ap, fp;
> - struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
> + struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
> u64 fraction[2], denominator;
> enum lru_list l;
> int noswap = 0;

You can save some patch lines by:
struct zone *zone = mz->zone;
and not doing zone => mz->zone changes that follow.

> @@ -1889,16 +1901,16 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc,
> goto out;
> }
>
> - anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
> - zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
> - file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
> - zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
> + anon = zone_nr_lru_pages(mz, LRU_ACTIVE_ANON) +
> + zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
> + file = zone_nr_lru_pages(mz, LRU_ACTIVE_FILE) +
> + zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
>
> if (global_reclaim(sc)) {
> - free = zone_page_state(zone, NR_FREE_PAGES);
> + free = zone_page_state(mz->zone, NR_FREE_PAGES);
> /* If we have very few page cache pages,
> force-scan anon pages. */
> - if (unlikely(file + free <= high_wmark_pages(zone))) {
> + if (unlikely(file + free <= high_wmark_pages(mz->zone))) {
> fraction[0] = 1;
> fraction[1] = 0;
> denominator = 1;
[...]
> @@ -2390,6 +2413,18 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
> }
> #endif
>
> +static void age_active_anon(struct zone *zone, struct scan_control *sc,
> + int priority)
> +{
> + struct mem_cgroup_zone mz = {
> + .mem_cgroup = NULL,
> + .zone = zone,
> + };
> +
> + if (inactive_anon_is_low(&mz))
> + shrink_active_list(SWAP_CLUSTER_MAX, &mz, sc, priority, 0);
> +}
> +

I do not like this very much because we are using a similar construct in
shrink_mem_cgroup_zone so we are duplicating that code.
What about adding age_mem_cgroup_active_anon (something like shrink_zone).

> /*
> * pgdat_balanced is used when checking if a node is balanced for high-order
> * allocations. Only zones that meet watermarks and are in a zone allowed
> @@ -2510,7 +2545,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
> */
> .nr_to_reclaim = ULONG_MAX,
> .order = order,
> - .mem_cgroup = NULL,
> + .target_mem_cgroup = NULL,
> };
> struct shrink_control shrink = {
> .gfp_mask = sc.gfp_mask,
> @@ -2549,9 +2584,7 @@ loop_again:
> * Do some background aging of the anon list, to give
> * pages a chance to be referenced before reclaiming.
> */
> - if (inactive_anon_is_low(zone, &sc))
> - shrink_active_list(SWAP_CLUSTER_MAX, zone,
> - &sc, priority, 0);
> + age_active_anon(zone, &sc, priority);
>
> if (!zone_watermark_ok_safe(zone, order,
> high_wmark_pages(zone), 0, 0)) {

--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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