On Sun 21-01-24 21:44:12, T.J. Mercier wrote: > This reverts commit 0388536ac29104a478c79b3869541524caec28eb. > > Proactive reclaim on the root cgroup is 10x slower after this patch when > MGLRU is enabled, and completion times for proactive reclaim on much > smaller non-root cgroups take ~30% longer (with or without MGLRU). What is the reclaim target in these pro-active reclaim requests? > With > root reclaim before the patch, I observe average reclaim rates of > ~70k pages/sec before try_to_free_mem_cgroup_pages starts to fail and > the nr_retries counter starts to decrement, eventually ending the > proactive reclaim attempt. Do I understand correctly that the reclaim target is over estimated and you expect that the reclaim process breaks out early> > After the patch the reclaim rate is > consistently ~6.6k pages/sec due to the reduced nr_pages value causing > scan aborts as soon as SWAP_CLUSTER_MAX pages are reclaimed. The > proactive reclaim doesn't complete after several minutes because > try_to_free_mem_cgroup_pages is still capable of reclaiming pages in > tiny SWAP_CLUSTER_MAX page chunks and nr_retries is never decremented. I do not understand this part. How does a smaller reclaim target manages to have reclaimed > 0 while larger one doesn't? > The docs for memory.reclaim say, "the kernel can over or under reclaim > from the target cgroup" which this patch was trying to fix. Revert it > until a less costly solution is found. > > Signed-off-by: T.J. Mercier <tjmercier@xxxxxxxxxx> > --- > mm/memcontrol.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index e4c8735e7c85..cee536c97151 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6956,8 +6956,8 @@ static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf, > lru_add_drain_all(); > > reclaimed = try_to_free_mem_cgroup_pages(memcg, > - min(nr_to_reclaim - nr_reclaimed, SWAP_CLUSTER_MAX), > - GFP_KERNEL, reclaim_options); > + nr_to_reclaim - nr_reclaimed, > + GFP_KERNEL, reclaim_options); > > if (!reclaimed && !nr_retries--) > return -EAGAIN; > -- > 2.43.0.429.g432eaa2c6b-goog > -- Michal Hocko SUSE Labs
