From: Jacob Wen <jian.w.wen@oracle.com>
To: Michal Hocko <mhocko@suse.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org
Subject: Re: [PATCH] mm/vmscan: DRY cleanup for do_try_to_free_pages()
Date: Sat, 19 Dec 2020 01:41:07 +0800 [thread overview]
Message-ID: <63e8a821-a3f6-47a6-f438-b27c32f4a05f@oracle.com> (raw)
In-Reply-To: <20201218142717.GA32193@dhcp22.suse.cz>
On 12/18/20 10:27 PM, Michal Hocko wrote:
> 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.
set_task_reclaim_state() is a function with 3 lines of code of which 2
lines contain WARN_ON_ONCE.
I am not comfortable with the current repetition.
>
>>>> Signed-off-by: Jacob Wen <jian.w.wen@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
>>>>
next prev parent reply other threads:[~2020-12-18 17:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 10:22 [PATCH] mm/vmscan: DRY cleanup for do_try_to_free_pages() Jacob Wen
2020-12-18 10:51 ` Michal Hocko
2020-12-18 13:51 ` Jacob Wen
2020-12-18 14:27 ` Michal Hocko
2020-12-18 17:41 ` Jacob Wen [this message]
2020-12-19 1:21 ` Chris Down
2020-12-19 3:18 ` Jacob Wen
2020-12-18 12:17 ` Matthew Wilcox
2020-12-18 13:54 ` Jacob Wen
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