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Message-ID: <20191025144144.GB386981@cmpxchg.org>
Date: Fri, 25 Oct 2019 10:41:44 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Roman Gushchin <guro@...com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Michal Hocko <mhocko@...e.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH 8/8] mm: vmscan: harmonize writeback congestion tracking
for nodes & memcgs
On Tue, Oct 22, 2019 at 09:03:57PM +0000, Roman Gushchin wrote:
> On Tue, Oct 22, 2019 at 10:48:03AM -0400, Johannes Weiner wrote:
> > The current writeback congestion tracking has separate flags for
> > kswapd reclaim (node level) and cgroup limit reclaim (memcg-node
> > level). This is unnecessarily complicated: the lruvec is an existing
> > abstraction layer for that node-memcg intersection.
> >
> > Introduce lruvec->flags and LRUVEC_CONGESTED. Then track that at the
> > reclaim root level, which is either the NUMA node for global reclaim,
> > or the cgroup-node intersection for cgroup reclaim.
>
> Good idea!
>
> Reviewed-by: Roman Gushchin <guro@...com>
Thank you.
The suggested cleanup fixlet for patch 7 causes conflicts in this
one. Here is the rebased version:
---
>From 253729a7639780508b166e547d13fa7894987a87 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@...xchg.org>
Date: Mon, 11 Mar 2019 15:43:44 -0400
Subject: [PATCH] mm: vmscan: harmonize writeback congestion tracking for
nodes & memcgs
The current writeback congestion tracking has separate flags for
kswapd reclaim (node level) and cgroup limit reclaim (memcg-node
level). This is unnecessarily complicated: the lruvec is an existing
abstraction layer for that node-memcg intersection.
Introduce lruvec->flags and LRUVEC_CONGESTED. Then track that at the
reclaim root level, which is either the NUMA node for global reclaim,
or the cgroup-node intersection for cgroup reclaim.
Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
include/linux/memcontrol.h | 6 +--
include/linux/mmzone.h | 11 +++--
mm/vmscan.c | 84 ++++++++++++--------------------------
3 files changed, 37 insertions(+), 64 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 498cea07cbb1..d8ffcf60440c 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -133,9 +133,6 @@ struct mem_cgroup_per_node {
unsigned long usage_in_excess;/* Set to the value by which */
/* the soft limit is exceeded*/
bool on_tree;
- bool congested; /* memcg has many dirty pages */
- /* backed by a congested BDI */
-
struct mem_cgroup *memcg; /* Back pointer, we cannot */
/* use container_of */
};
@@ -412,6 +409,9 @@ static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
goto out;
}
+ if (!memcg)
+ memcg = root_mem_cgroup;
+
mz = mem_cgroup_nodeinfo(memcg, pgdat->node_id);
lruvec = &mz->lruvec;
out:
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 449a44171026..c04b4c1f01fa 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -296,6 +296,12 @@ struct zone_reclaim_stat {
unsigned long recent_scanned[2];
};
+enum lruvec_flags {
+ LRUVEC_CONGESTED, /* lruvec has many dirty pages
+ * backed by a congested BDI
+ */
+};
+
struct lruvec {
struct list_head lists[NR_LRU_LISTS];
struct zone_reclaim_stat reclaim_stat;
@@ -303,6 +309,8 @@ struct lruvec {
atomic_long_t inactive_age;
/* Refaults at the time of last reclaim cycle */
unsigned long refaults;
+ /* Various lruvec state flags (enum lruvec_flags) */
+ unsigned long flags;
#ifdef CONFIG_MEMCG
struct pglist_data *pgdat;
#endif
@@ -572,9 +580,6 @@ struct zone {
} ____cacheline_internodealigned_in_smp;
enum pgdat_flags {
- PGDAT_CONGESTED, /* pgdat has many dirty pages backed by
- * a congested BDI
- */
PGDAT_DIRTY, /* reclaim scanning has recently found
* many dirty file pages at the tail
* of the LRU.
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6199692af434..47b5c5548f3a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -267,29 +267,6 @@ static bool writeback_throttling_sane(struct scan_control *sc)
#endif
return false;
}
-
-static void set_memcg_congestion(pg_data_t *pgdat,
- struct mem_cgroup *memcg,
- bool congested)
-{
- struct mem_cgroup_per_node *mn;
-
- if (!memcg)
- return;
-
- mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id);
- WRITE_ONCE(mn->congested, congested);
-}
-
-static bool memcg_congested(pg_data_t *pgdat,
- struct mem_cgroup *memcg)
-{
- struct mem_cgroup_per_node *mn;
-
- mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id);
- return READ_ONCE(mn->congested);
-
-}
#else
static int prealloc_memcg_shrinker(struct shrinker *shrinker)
{
@@ -309,18 +286,6 @@ static bool writeback_throttling_sane(struct scan_control *sc)
{
return true;
}
-
-static inline void set_memcg_congestion(struct pglist_data *pgdat,
- struct mem_cgroup *memcg, bool congested)
-{
-}
-
-static inline bool memcg_congested(struct pglist_data *pgdat,
- struct mem_cgroup *memcg)
-{
- return false;
-
-}
#endif
/*
@@ -2716,12 +2681,6 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
return inactive_lru_pages > pages_for_compaction;
}
-static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg)
-{
- return test_bit(PGDAT_CONGESTED, &pgdat->flags) ||
- (memcg && memcg_congested(pgdat, memcg));
-}
-
static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
{
struct mem_cgroup *target_memcg = sc->target_mem_cgroup;
@@ -2783,10 +2742,12 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
{
struct reclaim_state *reclaim_state = current->reclaim_state;
- struct mem_cgroup *target_memcg = sc->target_mem_cgroup;
unsigned long nr_reclaimed, nr_scanned;
+ struct lruvec *target_lruvec;
bool reclaimable = false;
+ target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
+
again:
memset(&sc->nr, 0, sizeof(sc->nr));
@@ -2801,7 +2762,7 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
}
/* Record the subtree's reclaim efficiency */
- vmpressure(sc->gfp_mask, target_memcg, true,
+ vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
sc->nr_scanned - nr_scanned,
sc->nr_reclaimed - nr_reclaimed);
@@ -2829,14 +2790,6 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
set_bit(PGDAT_WRITEBACK, &pgdat->flags);
- /*
- * Tag a node as congested if all the dirty pages
- * scanned were backed by a congested BDI and
- * wait_iff_congested will stall.
- */
- if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
- set_bit(PGDAT_CONGESTED, &pgdat->flags);
-
/* Allow kswapd to start writing pages during reclaim.*/
if (sc->nr.unqueued_dirty == sc->nr.file_taken)
set_bit(PGDAT_DIRTY, &pgdat->flags);
@@ -2852,12 +2805,17 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
}
/*
+ * Tag a node/memcg as congested if all the dirty pages
+ * scanned were backed by a congested BDI and
+ * wait_iff_congested will stall.
+ *
* Legacy memcg will stall in page writeback so avoid forcibly
* stalling in wait_iff_congested().
*/
- if (cgroup_reclaim(sc) && writeback_throttling_sane(sc) &&
+ if ((current_is_kswapd() ||
+ (cgroup_reclaim(sc) && writeback_throttling_sane(sc))) &&
sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
- set_memcg_congestion(pgdat, target_memcg, true);
+ set_bit(LRUVEC_CONGESTED, &target_lruvec->flags);
/*
* Stall direct reclaim for IO completions if underlying BDIs
@@ -2865,9 +2823,9 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
* starts encountering unqueued dirty pages or cycling through
* the LRU too quickly.
*/
- if (!sc->hibernation_mode && !current_is_kswapd() &&
- current_may_throttle() &&
- pgdat_memcg_congested(pgdat, target_memcg))
+ if (!current_is_kswapd() && current_may_throttle() &&
+ !sc->hibernation_mode &&
+ test_bit(LRUVEC_CONGESTED, &target_lruvec->flags))
wait_iff_congested(BLK_RW_ASYNC, HZ/10);
if (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
@@ -3081,8 +3039,16 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
if (zone->zone_pgdat == last_pgdat)
continue;
last_pgdat = zone->zone_pgdat;
+
snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat);
- set_memcg_congestion(last_pgdat, sc->target_mem_cgroup, false);
+
+ if (cgroup_reclaim(sc)) {
+ struct lruvec *lruvec;
+
+ lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup,
+ zone->zone_pgdat);
+ clear_bit(LRUVEC_CONGESTED, &lruvec->flags);
+ }
}
delayacct_freepages_end();
@@ -3462,7 +3428,9 @@ static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
/* Clear pgdat state for congested, dirty or under writeback. */
static void clear_pgdat_congested(pg_data_t *pgdat)
{
- clear_bit(PGDAT_CONGESTED, &pgdat->flags);
+ struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat);
+
+ clear_bit(LRUVEC_CONGESTED, &lruvec->flags);
clear_bit(PGDAT_DIRTY, &pgdat->flags);
clear_bit(PGDAT_WRITEBACK, &pgdat->flags);
}
--
2.23.0
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