The patch titled
Subject: mm: workingset: tell cache transitions from workingset thrashing
has been added to the -mm tree. Its filename is
mm-workingset-tell-cache-transitions-from-workingset-thrashing.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-workingset-tell-cache-transitions-from-workingset-thrashing.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-workingset-tell-cache-transitions-from-workingset-thrashing.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: mm: workingset: tell cache transitions from workingset thrashing
Refaults happen during transitions between workingsets as well as in-place
thrashing. Knowing the difference between the two has a range of
applications, including measuring the impact of memory shortage on the
system performance, as well as the ability to smarter balance pressure
between the filesystem cache and the swap-backed workingset.
During workingset transitions, inactive cache refaults and pushes out
established active cache. When that active cache isn't stale, however,
and also ends up refaulting, that's bonafide thrashing.
Introduce a new page flag that tells on eviction whether the page has been
active or not in its lifetime. This bit is then stored in the shadow
entry, to classify refaults as transitioning or thrashing.
How many page->flags does this leave us with on 32-bit?
20 bits are always page flags
21 if you have an MMU
23 with the zone bits for DMA, Normal, HighMem, Movable
29 with the sparsemem section bits
30 if PAE is enabled
31 with this patch.
So on 32-bit PAE, that leaves 1 bit for distinguishing two NUMA nodes. If
that's not enough, the system can switch to discontigmem and re-gain the 6
or 7 sparsemem section bits.
Link: http://lkml.kernel.org/r/20180712172942.10094-3-hannes@xxxxxxxxxxx
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Christopher Lameter <cl@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Johannes Weiner <jweiner@xxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN include/linux/mmzone.h~mm-workingset-tell-cache-transitions-from-workingset-thrashing include/linux/mmzone.h
--- a/include/linux/mmzone.h~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/include/linux/mmzone.h
@@ -163,6 +163,7 @@ enum node_stat_item {
NR_ISOLATED_FILE, /* Temporary isolated pages from file lru */
WORKINGSET_REFAULT,
WORKINGSET_ACTIVATE,
+ WORKINGSET_RESTORE,
WORKINGSET_NODERECLAIM,
NR_ANON_MAPPED, /* Mapped anonymous pages */
NR_FILE_MAPPED, /* pagecache pages mapped into pagetables.
diff -puN include/linux/page-flags.h~mm-workingset-tell-cache-transitions-from-workingset-thrashing include/linux/page-flags.h
--- a/include/linux/page-flags.h~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/include/linux/page-flags.h
@@ -69,13 +69,14 @@
*/
enum pageflags {
PG_locked, /* Page is locked. Don't touch. */
- PG_error,
PG_referenced,
PG_uptodate,
PG_dirty,
PG_lru,
PG_active,
+ PG_workingset,
PG_waiters, /* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */
+ PG_error,
PG_slab,
PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
PG_arch_1,
@@ -280,6 +281,8 @@ PAGEFLAG(Dirty, dirty, PF_HEAD) TESTSCFL
PAGEFLAG(LRU, lru, PF_HEAD) __CLEARPAGEFLAG(LRU, lru, PF_HEAD)
PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
TESTCLEARFLAG(Active, active, PF_HEAD)
+PAGEFLAG(Workingset, workingset, PF_HEAD)
+ TESTCLEARFLAG(Workingset, workingset, PF_HEAD)
__PAGEFLAG(Slab, slab, PF_NO_TAIL)
__PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL)
PAGEFLAG(Checked, checked, PF_NO_COMPOUND) /* Used by some filesystems */
diff -puN include/linux/swap.h~mm-workingset-tell-cache-transitions-from-workingset-thrashing include/linux/swap.h
--- a/include/linux/swap.h~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/include/linux/swap.h
@@ -296,7 +296,7 @@ struct vma_swap_readahead {
/* linux/mm/workingset.c */
void *workingset_eviction(struct address_space *mapping, struct page *page);
-bool workingset_refault(void *shadow);
+void workingset_refault(struct page *page, void *shadow);
void workingset_activation(struct page *page);
/* Do not use directly, use workingset_lookup_update */
diff -puN include/trace/events/mmflags.h~mm-workingset-tell-cache-transitions-from-workingset-thrashing include/trace/events/mmflags.h
--- a/include/trace/events/mmflags.h~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/include/trace/events/mmflags.h
@@ -88,6 +88,7 @@
{1UL << PG_dirty, "dirty" }, \
{1UL << PG_lru, "lru" }, \
{1UL << PG_active, "active" }, \
+ {1UL << PG_workingset, "workingset" }, \
{1UL << PG_slab, "slab" }, \
{1UL << PG_owner_priv_1, "owner_priv_1" }, \
{1UL << PG_arch_1, "arch_1" }, \
diff -puN mm/filemap.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing mm/filemap.c
--- a/mm/filemap.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/mm/filemap.c
@@ -915,12 +915,9 @@ int add_to_page_cache_lru(struct page *p
* data from the working set, only to cache data that will
* get overwritten with something else, is a waste of memory.
*/
- if (!(gfp_mask & __GFP_WRITE) &&
- shadow && workingset_refault(shadow)) {
- SetPageActive(page);
- workingset_activation(page);
- } else
- ClearPageActive(page);
+ WARN_ON_ONCE(PageActive(page));
+ if (!(gfp_mask & __GFP_WRITE) && shadow)
+ workingset_refault(page, shadow);
lru_cache_add(page);
}
return ret;
diff -puN mm/huge_memory.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing mm/huge_memory.c
--- a/mm/huge_memory.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/mm/huge_memory.c
@@ -2368,6 +2368,7 @@ static void __split_huge_page_tail(struc
(1L << PG_mlocked) |
(1L << PG_uptodate) |
(1L << PG_active) |
+ (1L << PG_workingset) |
(1L << PG_locked) |
(1L << PG_unevictable) |
(1L << PG_dirty)));
diff -puN mm/memcontrol.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing mm/memcontrol.c
--- a/mm/memcontrol.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/mm/memcontrol.c
@@ -5554,6 +5554,8 @@ static int memory_stat_show(struct seq_f
stat[WORKINGSET_REFAULT]);
seq_printf(m, "workingset_activate %lu\n",
stat[WORKINGSET_ACTIVATE]);
+ seq_printf(m, "workingset_restore %lu\n",
+ stat[WORKINGSET_RESTORE]);
seq_printf(m, "workingset_nodereclaim %lu\n",
stat[WORKINGSET_NODERECLAIM]);
diff -puN mm/migrate.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing mm/migrate.c
--- a/mm/migrate.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/mm/migrate.c
@@ -682,6 +682,8 @@ void migrate_page_states(struct page *ne
SetPageActive(newpage);
} else if (TestClearPageUnevictable(page))
SetPageUnevictable(newpage);
+ if (PageWorkingset(page))
+ SetPageWorkingset(newpage);
if (PageChecked(page))
SetPageChecked(newpage);
if (PageMappedToDisk(page))
diff -puN mm/swap_state.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing mm/swap_state.c
--- a/mm/swap_state.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/mm/swap_state.c
@@ -448,6 +448,7 @@ struct page *__read_swap_cache_async(swp
/*
* Initiate read into locked page and return.
*/
+ SetPageWorkingset(new_page);
lru_cache_add_anon(new_page);
*new_page_allocated = true;
return new_page;
diff -puN mm/vmscan.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing mm/vmscan.c
--- a/mm/vmscan.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/mm/vmscan.c
@@ -2135,6 +2135,7 @@ static void shrink_active_list(unsigned
}
ClearPageActive(page); /* we are de-activating */
+ SetPageWorkingset(page);
list_add(&page->lru, &l_inactive);
}
diff -puN mm/vmstat.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing mm/vmstat.c
--- a/mm/vmstat.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/mm/vmstat.c
@@ -1145,6 +1145,7 @@ const char * const vmstat_text[] = {
"nr_isolated_file",
"workingset_refault",
"workingset_activate",
+ "workingset_restore",
"workingset_nodereclaim",
"nr_anon_pages",
"nr_mapped",
diff -puN mm/workingset.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing mm/workingset.c
--- a/mm/workingset.c~mm-workingset-tell-cache-transitions-from-workingset-thrashing
+++ a/mm/workingset.c
@@ -121,7 +121,7 @@
* the only thing eating into inactive list space is active pages.
*
*
- * Activating refaulting pages
+ * Refaulting inactive pages
*
* All that is known about the active list is that the pages have been
* accessed more than once in the past. This means that at any given
@@ -134,6 +134,10 @@
* used less frequently than the refaulting page - or even not used at
* all anymore.
*
+ * That means if inactive cache is refaulting with a suitable refault
+ * distance, we assume the cache workingset is transitioning and put
+ * pressure on the current active list.
+ *
* If this is wrong and demotion kicks in, the pages which are truly
* used more frequently will be reactivated while the less frequently
* used once will be evicted from memory.
@@ -141,6 +145,14 @@
* But if this is right, the stale pages will be pushed out of memory
* and the used pages get to stay in cache.
*
+ * Refaulting active pages
+ *
+ * If on the other hand the refaulting pages have recently been
+ * deactivated, it means that the active list is no longer protecting
+ * actively used cache from reclaim. The cache is NOT transitioning to
+ * a different workingset; the existing workingset is thrashing in the
+ * space allocated to the page cache.
+ *
*
* Implementation
*
@@ -156,8 +168,7 @@
*/
#define EVICTION_SHIFT (RADIX_TREE_EXCEPTIONAL_ENTRY + \
- NODES_SHIFT + \
- MEM_CGROUP_ID_SHIFT)
+ 1 + NODES_SHIFT + MEM_CGROUP_ID_SHIFT)
#define EVICTION_MASK (~0UL >> EVICTION_SHIFT)
/*
@@ -170,23 +181,28 @@
*/
static unsigned int bucket_order __read_mostly;
-static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction)
+static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction,
+ bool workingset)
{
eviction >>= bucket_order;
eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
eviction = (eviction << NODES_SHIFT) | pgdat->node_id;
+ eviction = (eviction << 1) | workingset;
eviction = (eviction << RADIX_TREE_EXCEPTIONAL_SHIFT);
return (void *)(eviction | RADIX_TREE_EXCEPTIONAL_ENTRY);
}
static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat,
- unsigned long *evictionp)
+ unsigned long *evictionp, bool *workingsetp)
{
unsigned long entry = (unsigned long)shadow;
int memcgid, nid;
+ bool workingset;
entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
+ workingset = entry & 1;
+ entry >>= 1;
nid = entry & ((1UL << NODES_SHIFT) - 1);
entry >>= NODES_SHIFT;
memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);
@@ -195,6 +211,7 @@ static void unpack_shadow(void *shadow,
*memcgidp = memcgid;
*pgdat = NODE_DATA(nid);
*evictionp = entry << bucket_order;
+ *workingsetp = workingset;
}
/**
@@ -207,8 +224,8 @@ static void unpack_shadow(void *shadow,
*/
void *workingset_eviction(struct address_space *mapping, struct page *page)
{
- struct mem_cgroup *memcg = page_memcg(page);
struct pglist_data *pgdat = page_pgdat(page);
+ struct mem_cgroup *memcg = page_memcg(page);
int memcgid = mem_cgroup_id(memcg);
unsigned long eviction;
struct lruvec *lruvec;
@@ -220,30 +237,30 @@ void *workingset_eviction(struct address
lruvec = mem_cgroup_lruvec(pgdat, memcg);
eviction = atomic_long_inc_return(&lruvec->inactive_age);
- return pack_shadow(memcgid, pgdat, eviction);
+ return pack_shadow(memcgid, pgdat, eviction, PageWorkingset(page));
}
/**
* workingset_refault - evaluate the refault of a previously evicted page
+ * @page: the freshly allocated replacement page
* @shadow: shadow entry of the evicted page
*
* Calculates and evaluates the refault distance of the previously
* evicted page in the context of the node it was allocated in.
- *
- * Returns %true if the page should be activated, %false otherwise.
*/
-bool workingset_refault(void *shadow)
+void workingset_refault(struct page *page, void *shadow)
{
unsigned long refault_distance;
+ struct pglist_data *pgdat;
unsigned long active_file;
struct mem_cgroup *memcg;
unsigned long eviction;
struct lruvec *lruvec;
unsigned long refault;
- struct pglist_data *pgdat;
+ bool workingset;
int memcgid;
- unpack_shadow(shadow, &memcgid, &pgdat, &eviction);
+ unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset);
rcu_read_lock();
/*
@@ -263,41 +280,51 @@ bool workingset_refault(void *shadow)
* configurations instead.
*/
memcg = mem_cgroup_from_id(memcgid);
- if (!mem_cgroup_disabled() && !memcg) {
- rcu_read_unlock();
- return false;
- }
+ if (!mem_cgroup_disabled() && !memcg)
+ goto out;
lruvec = mem_cgroup_lruvec(pgdat, memcg);
refault = atomic_long_read(&lruvec->inactive_age);
active_file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES);
/*
- * The unsigned subtraction here gives an accurate distance
- * across inactive_age overflows in most cases.
+ * Calculate the refault distance
*
- * There is a special case: usually, shadow entries have a
- * short lifetime and are either refaulted or reclaimed along
- * with the inode before they get too old. But it is not
- * impossible for the inactive_age to lap a shadow entry in
- * the field, which can then can result in a false small
- * refault distance, leading to a false activation should this
- * old entry actually refault again. However, earlier kernels
- * used to deactivate unconditionally with *every* reclaim
- * invocation for the longest time, so the occasional
- * inappropriate activation leading to pressure on the active
- * list is not a problem.
+ * The unsigned subtraction here gives an accurate distance
+ * across inactive_age overflows in most cases. There is a
+ * special case: usually, shadow entries have a short lifetime
+ * and are either refaulted or reclaimed along with the inode
+ * before they get too old. But it is not impossible for the
+ * inactive_age to lap a shadow entry in the field, which can
+ * then can result in a false small refault distance, leading
+ * to a false activation should this old entry actually
+ * refault again. However, earlier kernels used to deactivate
+ * unconditionally with *every* reclaim invocation for the
+ * longest time, so the occasional inappropriate activation
+ * leading to pressure on the active list is not a problem.
*/
refault_distance = (refault - eviction) & EVICTION_MASK;
inc_lruvec_state(lruvec, WORKINGSET_REFAULT);
- if (refault_distance <= active_file) {
- inc_lruvec_state(lruvec, WORKINGSET_ACTIVATE);
- rcu_read_unlock();
- return true;
+ /*
+ * Compare the distance to the existing workingset size. We
+ * don't act on pages that couldn't stay resident even if all
+ * the memory was available to the page cache.
+ */
+ if (refault_distance > active_file)
+ goto out;
+
+ SetPageActive(page);
+ atomic_long_inc(&lruvec->inactive_age);
+ inc_lruvec_state(lruvec, WORKINGSET_ACTIVATE);
+
+ /* Page was active prior to eviction */
+ if (workingset) {
+ SetPageWorkingset(page);
+ inc_lruvec_state(lruvec, WORKINGSET_RESTORE);
}
+out:
rcu_read_unlock();
- return false;
}
/**
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
mm-workingset-tell-cache-transitions-from-workingset-thrashing.patch
delayacct-track-delays-from-thrashing-cache-pages.patch
sched-loadavg-consolidate-load_int-load_frac-calc_load.patch
sched-loadavg-make-calc_load_n-public.patch
sched-schedh-make-rq-locking-and-clock-functions-available-in-statsh.patch
sched-introduce-this_rq_lock_irq.patch
psi-pressure-stall-information-for-cpu-memory-and-io.patch
psi-cgroup-support.patch
psi-aggregate-ongoing-stall-events-when-somebody-reads-pressure.patch
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