| Message ID | 20230328061638.203420-9-yosryahmed@google.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | memcg: make rstat flushing irq and sleep friendly | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On Mon, Mar 27, 2023 at 11:16 PM Yosry Ahmed <yosryahmed@google.com> wrote: > > Memory reclaim is a sleepable context. Allow sleeping when flushing > memcg stats to avoid unnecessarily performing a lot of work without > sleeping. This can slow down reclaim code if flushing stats is taking > too long, but there is already multiple cond_resched()'s in reclaim > code. > > Signed-off-by: Yosry Ahmed <yosryahmed@google.com> Acked-by: Shakeel Butt <shakeelb@google.com> > --- > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index a9511ccb936f..9c1c5e8b24b8 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2845,7 +2845,7 @@ static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc) > * Flush the memory cgroup stats, so that we read accurate per-memcg > * lruvec stats for heuristics. > */ > - mem_cgroup_flush_stats_atomic(); > + mem_cgroup_flush_stats(); I wonder if we should just replace this with mem_cgroup_flush_stats_ratelimited().
On Tue, Mar 28, 2023 at 06:16:37AM +0000, Yosry Ahmed wrote: > Memory reclaim is a sleepable context. Allow sleeping when flushing > memcg stats to avoid unnecessarily performing a lot of work without > sleeping. This can slow down reclaim code if flushing stats is taking > too long, but there is already multiple cond_resched()'s in reclaim > code. > > Signed-off-by: Yosry Ahmed <yosryahmed@google.com> Forget what I said about this in the previous patch. :) Acked-by: Johannes Weiner <hannes@cmpxchg.org>
On Tue, Mar 28, 2023 at 8:19 AM Shakeel Butt <shakeelb@google.com> wrote: > > On Mon, Mar 27, 2023 at 11:16 PM Yosry Ahmed <yosryahmed@google.com> wrote: > > > > Memory reclaim is a sleepable context. Allow sleeping when flushing > > memcg stats to avoid unnecessarily performing a lot of work without > > sleeping. This can slow down reclaim code if flushing stats is taking > > too long, but there is already multiple cond_resched()'s in reclaim > > code. > > > > Signed-off-by: Yosry Ahmed <yosryahmed@google.com> > > Acked-by: Shakeel Butt <shakeelb@google.com> > > > --- > > mm/vmscan.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index a9511ccb936f..9c1c5e8b24b8 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -2845,7 +2845,7 @@ static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc) > > * Flush the memory cgroup stats, so that we read accurate per-memcg > > * lruvec stats for heuristics. > > */ > > - mem_cgroup_flush_stats_atomic(); > > + mem_cgroup_flush_stats(); > > I wonder if we should just replace this with > mem_cgroup_flush_stats_ratelimited(). Thanks for taking a look! I was hesitant about doing this because the flush call is inside the retry loop, and it seems like we want to get fresh stats on each retry. It seems very likely that we end up not flushing between retries with mem_cgroup_flush_stats_ratelimited(). Maybe change it if we observe problems with non-atomic flushing?
On Tue, Mar 28, 2023 at 12:02 PM Yosry Ahmed <yosryahmed@google.com> wrote: > > On Tue, Mar 28, 2023 at 8:19 AM Shakeel Butt <shakeelb@google.com> wrote: > > > > On Mon, Mar 27, 2023 at 11:16 PM Yosry Ahmed <yosryahmed@google.com> wrote: > > > > > > Memory reclaim is a sleepable context. Allow sleeping when flushing > > > memcg stats to avoid unnecessarily performing a lot of work without > > > sleeping. This can slow down reclaim code if flushing stats is taking > > > too long, but there is already multiple cond_resched()'s in reclaim > > > code. > > > > > > Signed-off-by: Yosry Ahmed <yosryahmed@google.com> > > > > Acked-by: Shakeel Butt <shakeelb@google.com> > > > > > --- > > > mm/vmscan.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > index a9511ccb936f..9c1c5e8b24b8 100644 > > > --- a/mm/vmscan.c > > > +++ b/mm/vmscan.c > > > @@ -2845,7 +2845,7 @@ static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc) > > > * Flush the memory cgroup stats, so that we read accurate per-memcg > > > * lruvec stats for heuristics. > > > */ > > > - mem_cgroup_flush_stats_atomic(); > > > + mem_cgroup_flush_stats(); > > > > I wonder if we should just replace this with > > mem_cgroup_flush_stats_ratelimited(). > > Thanks for taking a look! > > I was hesitant about doing this because the flush call is inside the > retry loop, and it seems like we want to get fresh stats on each > retry. It seems very likely that we end up not flushing between > retries with mem_cgroup_flush_stats_ratelimited(). > > Maybe change it if we observe problems with non-atomic flushing? Yeah, let's leave it for the future if we see the issue.
diff --git a/mm/vmscan.c b/mm/vmscan.c index a9511ccb936f..9c1c5e8b24b8 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2845,7 +2845,7 @@ static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc) * Flush the memory cgroup stats, so that we read accurate per-memcg * lruvec stats for heuristics. */ - mem_cgroup_flush_stats_atomic(); + mem_cgroup_flush_stats(); /* * Determine the scan balance between anon and file LRUs.
Memory reclaim is a sleepable context. Allow sleeping when flushing memcg stats to avoid unnecessarily performing a lot of work without sleeping. This can slow down reclaim code if flushing stats is taking too long, but there is already multiple cond_resched()'s in reclaim code. Signed-off-by: Yosry Ahmed <yosryahmed@google.com> --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)