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From: Vladimir Davydov <vdavydov.dev@gmail.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: akpm@linux-foundation.org, shakeelb@google.com,
	viro@zeniv.linux.org.uk, hannes@cmpxchg.org, mhocko@kernel.org,
	tglx@linutronix.de, pombredanne@nexb.com,
	stummala@codeaurora.org, gregkh@linuxfoundation.org,
	sfr@canb.auug.org.au, guro@fb.com, mka@chromium.org,
	penguin-kernel@I-love.SAKURA.ne.jp, chris@chris-wilson.co.uk,
	longman@redhat.com, minchan@kernel.org, ying.huang@intel.com,
	mgorman@techsingularity.net, jbacik@fb.com, linux@roeck-us.net,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	willy@infradead.org, lirongqing@baidu.com,
	aryabinin@virtuozzo.com
Subject: Re: [PATCH v5 11/13] mm: Iterate only over charged shrinkers during memcg shrink_slab()
Date: Thu, 17 May 2018 16:51:21 +0300	[thread overview]
Message-ID: <20180517135121.wtaiuj6pqxzodrlr@esperanza> (raw)
In-Reply-To: <f2dec4fb-6107-5d6c-62b3-8b680895c5c1@virtuozzo.com>

On Thu, May 17, 2018 at 02:49:26PM +0300, Kirill Tkhai wrote:
> On 17.05.2018 07:16, Vladimir Davydov wrote:
> > On Tue, May 15, 2018 at 05:49:59PM +0300, Kirill Tkhai wrote:
> >>>> @@ -589,13 +647,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
> >>>>  			.memcg = memcg,
> >>>>  		};
> >>>>  
> >>>> -		/*
> >>>> -		 * If kernel memory accounting is disabled, we ignore
> >>>> -		 * SHRINKER_MEMCG_AWARE flag and call all shrinkers
> >>>> -		 * passing NULL for memcg.
> >>>> -		 */
> >>>> -		if (memcg_kmem_enabled() &&
> >>>> -		    !!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE))
> >>>> +		if (!!memcg != !!(shrinker->flags & SHRINKER_MEMCG_AWARE))
> >>>>  			continue;
> >>>
> >>> I want this check gone. It's easy to achieve, actually - just remove the
> >>> following lines from shrink_node()
> >>>
> >>> 		if (global_reclaim(sc))
> >>> 			shrink_slab(sc->gfp_mask, pgdat->node_id, NULL,
> >>> 				    sc->priority);
> >>
> >> This check is not related to the patchset.
> > 
> > Yes, it is. This patch modifies shrink_slab which is used only by
> > shrink_node. Simplifying shrink_node along the way looks right to me.
> 
> shrink_slab() is used not only in this place.

drop_slab_node() doesn't really count as it is an extract from shrink_node()

> I does not seem a trivial change for me.
> 
> >> Let's don't mix everything in the single series of patches, because
> >> after your last remarks it will grow at least up to 15 patches.
> > 
> > Most of which are trivial so I don't see any problem here.
> > 
> >> This patchset can't be responsible for everything.
> > 
> > I don't understand why you balk at simplifying the code a bit while you
> > are patching related functions anyway.
> 
> Because this function is used in several places, and we have some particulars
> on root_mem_cgroup initialization, and this function called from these places
> with different states of root_mem_cgroup. It does not seem trivial fix for me.

Let me do it for you then:

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9b697323a88c..e778569538de 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -486,10 +486,8 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
  * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
  * unaware shrinkers will receive a node id of 0 instead.
  *
- * @memcg specifies the memory cgroup to target. If it is not NULL,
- * only shrinkers with SHRINKER_MEMCG_AWARE set will be called to scan
- * objects from the memory cgroup specified. Otherwise, only unaware
- * shrinkers are called.
+ * @memcg specifies the memory cgroup to target. Unaware shrinkers
+ * are called only if it is the root cgroup.
  *
  * @priority is sc->priority, we take the number of objects and >> by priority
  * in order to get the scan target.
@@ -554,6 +552,7 @@ void drop_slab_node(int nid)
 		struct mem_cgroup *memcg = NULL;
 
 		freed = 0;
+		memcg = mem_cgroup_iter(NULL, NULL, NULL);
 		do {
 			freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
 		} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
@@ -2557,9 +2556,8 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 			shrink_node_memcg(pgdat, memcg, sc, &lru_pages);
 			node_lru_pages += lru_pages;
 
-			if (memcg)
-				shrink_slab(sc->gfp_mask, pgdat->node_id,
-					    memcg, sc->priority);
+			shrink_slab(sc->gfp_mask, pgdat->node_id,
+				    memcg, sc->priority);
 
 			/* Record the group's reclaim efficiency */
 			vmpressure(sc->gfp_mask, memcg, false,
@@ -2583,10 +2581,6 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 			}
 		} while ((memcg = mem_cgroup_iter(root, memcg, &reclaim)));
 
-		if (global_reclaim(sc))
-			shrink_slab(sc->gfp_mask, pgdat->node_id, NULL,
-				    sc->priority);
-
 		if (reclaim_state) {
 			sc->nr_reclaimed += reclaim_state->reclaimed_slab;
 			reclaim_state->reclaimed_slab = 0;


Seems simple enough to fold it into this patch, doesn't it?

  reply	other threads:[~2018-05-17 13:51 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-10  9:52 [PATCH v5 00/13] Improve shrink_slab() scalability (old complexity was O(n^2), new is O(n)) Kirill Tkhai
2018-05-10  9:52 ` [PATCH v5 01/13] mm: Assign id to every memcg-aware shrinker Kirill Tkhai
2018-05-13  5:15   ` Vladimir Davydov
2018-05-14  9:03     ` Kirill Tkhai
2018-05-15  3:29       ` Vladimir Davydov
2018-05-10  9:52 ` [PATCH v5 02/13] memcg: Move up for_each_mem_cgroup{, _tree} defines Kirill Tkhai
2018-05-10  9:52 ` [PATCH v5 03/13] mm: Assign memcg-aware shrinkers bitmap to memcg Kirill Tkhai
2018-05-13 16:47   ` Vladimir Davydov
2018-05-14  9:34     ` Kirill Tkhai
2018-05-15  3:54       ` Vladimir Davydov
2018-05-10  9:52 ` [PATCH v5 04/13] mm: Refactoring in workingset_init() Kirill Tkhai
2018-05-10  9:52 ` [PATCH v5 05/13] fs: Refactoring in alloc_super() Kirill Tkhai
2018-05-10  9:53 ` [PATCH v5 06/13] fs: Propagate shrinker::id to list_lru Kirill Tkhai
2018-05-13 16:57   ` Vladimir Davydov
2018-05-10  9:53 ` [PATCH v5 07/13] list_lru: Add memcg argument to list_lru_from_kmem() Kirill Tkhai
2018-05-10  9:53 ` [PATCH v5 08/13] list_lru: Pass dst_memcg argument to memcg_drain_list_lru_node() Kirill Tkhai
2018-05-10  9:53 ` [PATCH v5 09/13] list_lru: Pass lru " Kirill Tkhai
2018-05-10  9:53 ` [PATCH v5 10/13] mm: Set bit in memcg shrinker bitmap on first list_lru item apearance Kirill Tkhai
2018-05-15  4:08   ` Vladimir Davydov
2018-05-10  9:53 ` [PATCH v5 11/13] mm: Iterate only over charged shrinkers during memcg shrink_slab() Kirill Tkhai
2018-05-15  5:44   ` Vladimir Davydov
2018-05-15 10:12     ` Kirill Tkhai
2018-05-17  4:33       ` Vladimir Davydov
2018-05-17 11:39         ` Kirill Tkhai
2018-05-15 14:49     ` Kirill Tkhai
2018-05-17  4:16       ` Vladimir Davydov
2018-05-17 11:49         ` Kirill Tkhai
2018-05-17 13:51           ` Vladimir Davydov [this message]
2018-05-10  9:54 ` [PATCH v5 12/13] mm: Add SHRINK_EMPTY shrinker methods return value Kirill Tkhai
2018-05-10  9:54 ` [PATCH v5 13/13] mm: Clear shrinker bit if there are no objects related to memcg Kirill Tkhai
2018-05-15  5:59   ` Vladimir Davydov
2018-05-15  8:55     ` Kirill Tkhai
2018-05-17  4:49       ` Vladimir Davydov

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