On Fri 18-12-20 21:51:48, Jacob Wen wrote:
>
> On 12/18/20 6:51 PM, Michal Hocko wrote:
> > On Fri 18-12-20 18:22:17, Jacob Wen wrote:
> > > This patch reduces repetition of set_task_reclaim_state() around
> > > do_try_to_free_pages().
> > The changelog really should be talking about why this is needed/useful.
> > From the above it is not really clear whether you aimed at doing
> > a clean up or this is a fix for some misbehavior. I do assume the former
> > but this should be clearly articulated.
>
> How about this?
>
> mm/vmscan: remove duplicate code around do_try_to_free_pages()
>
> This patch moves set_task_reclaim_state() into do_try_to_free_pages()
> to avoid unnecessary repetition. It doesn't introduce functional
> change.
This is still more about what is changed more than why it is changed. I
would go with something like the following:
"
reclaim_state has to be set for all reclaim paths because it acts as a
storage to collect reclaim feedback. Currently set_task_reclaim_state is
called from each highlevel reclaim function. Simplify the code flow by
moving set_task_reclaim_state into core direct reclaim function
(do_try_to_free_pages) for all direct reclaim paths.
"
To the patch itself. I am not opposed but I do not see an urgent reason
to take it either. The net LOC increases slightly, it makes
do_try_to_free_pages slightly more tricky due to different early return
paths. Highlevel direct reclaim functions do not tend to change a lot.
> > > Signed-off-by: Jacob Wen <jian.w....@oracle.com>
> > > ---
> > > mm/vmscan.c | 27 ++++++++++++++++-----------
> > > 1 file changed, 16 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > index 257cba79a96d..4bc244b23686 100644
> > > --- a/mm/vmscan.c
> > > +++ b/mm/vmscan.c
> > > @@ -3023,6 +3023,10 @@ static unsigned long do_try_to_free_pages(struct
> > > zonelist *zonelist,
> > > pg_data_t *last_pgdat;
> > > struct zoneref *z;
> > > struct zone *zone;
> > > + unsigned long ret;
> > > +
> > > + set_task_reclaim_state(current, &sc->reclaim_state);
> > > +
> > > retry:
> > > delayacct_freepages_start();
> > > @@ -3069,12 +3073,16 @@ static unsigned long do_try_to_free_pages(struct
> > > zonelist *zonelist,
> > > delayacct_freepages_end();
> > > - if (sc->nr_reclaimed)
> > > - return sc->nr_reclaimed;
> > > + if (sc->nr_reclaimed) {
> > > + ret = sc->nr_reclaimed;
> > > + goto out;
> > > + }
> > > /* Aborted reclaim to try compaction? don't OOM, then */
> > > - if (sc->compaction_ready)
> > > - return 1;
> > > + if (sc->compaction_ready) {
> > > + ret = 1;
> > > + goto out;
> > > + }
> > > /*
> > > * We make inactive:active ratio decisions based on the node's
> > > @@ -3101,7 +3109,10 @@ static unsigned long do_try_to_free_pages(struct
> > > zonelist *zonelist,
> > > goto retry;
> > > }
> > > - return 0;
> > > + ret = 0;
> > > +out:
> > > + set_task_reclaim_state(current, NULL);
> > > + return ret;
> > > }
> > > static bool allow_direct_reclaim(pg_data_t *pgdat)
> > > @@ -3269,13 +3280,11 @@ unsigned long try_to_free_pages(struct zonelist
> > > *zonelist, int order,
> > > if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask))
> > > return 1;
> > > - set_task_reclaim_state(current, &sc.reclaim_state);
> > > trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask);
> > > nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
> > > trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
> > > - set_task_reclaim_state(current, NULL);
> > > return nr_reclaimed;
> > > }
> > > @@ -3347,7 +3356,6 @@ unsigned long try_to_free_mem_cgroup_pages(struct
> > > mem_cgroup *memcg,
> > > */
> > > struct zonelist *zonelist = node_zonelist(numa_node_id(),
> > > sc.gfp_mask);
> > > - set_task_reclaim_state(current, &sc.reclaim_state);
> > > trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask);
> > > noreclaim_flag = memalloc_noreclaim_save();
> > > @@ -3355,7 +3363,6 @@ unsigned long try_to_free_mem_cgroup_pages(struct
> > > mem_cgroup *memcg,
> > > memalloc_noreclaim_restore(noreclaim_flag);
> > > trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
> > > - set_task_reclaim_state(current, NULL);
> > > return nr_reclaimed;
> > > }
> > > @@ -4023,11 +4030,9 @@ unsigned long shrink_all_memory(unsigned long
> > > nr_to_reclaim)
> > > fs_reclaim_acquire(sc.gfp_mask);
> > > noreclaim_flag = memalloc_noreclaim_save();
> > > - set_task_reclaim_state(current, &sc.reclaim_state);
> > > nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
> > > - set_task_reclaim_state(current, NULL);
> > > memalloc_noreclaim_restore(noreclaim_flag);
> > > fs_reclaim_release(sc.gfp_mask);
> > > --
> > > 2.25.1
> > >
--
Michal Hocko
SUSE Labs
