summaryrefslogtreecommitdiff
path: root/mm/vmscan.c
diff options
context:
space:
mode:
authorJohannes Weiner <hannes@cmpxchg.org>2018-10-26 15:06:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-10-26 16:26:32 -0700
commiteb414681d5a07d28d2ff90dc05f69ec6b232ebd2 (patch)
tree69e37010954e597b404709ecd9a11b9f7373cf0f /mm/vmscan.c
parent246b3b3342c9b0a2e24cda2178be87bc36e1c874 (diff)
psi: pressure stall information for CPU, memory, and IO
When systems are overcommitted and resources become contended, it's hard to tell exactly the impact this has on workload productivity, or how close the system is to lockups and OOM kills. In particular, when machines work multiple jobs concurrently, the impact of overcommit in terms of latency and throughput on the individual job can be enormous. In order to maximize hardware utilization without sacrificing individual job health or risk complete machine lockups, this patch implements a way to quantify resource pressure in the system. A kernel built with CONFIG_PSI=y creates files in /proc/pressure/ that expose the percentage of time the system is stalled on CPU, memory, or IO, respectively. Stall states are aggregate versions of the per-task delay accounting delays: cpu: some tasks are runnable but not executing on a CPU memory: tasks are reclaiming, or waiting for swapin or thrashing cache io: tasks are waiting for io completions These percentages of walltime can be thought of as pressure percentages, and they give a general sense of system health and productivity loss incurred by resource overcommit. They can also indicate when the system is approaching lockup scenarios and OOMs. To do this, psi keeps track of the task states associated with each CPU and samples the time they spend in stall states. Every 2 seconds, the samples are averaged across CPUs - weighted by the CPUs' non-idle time to eliminate artifacts from unused CPUs - and translated into percentages of walltime. A running average of those percentages is maintained over 10s, 1m, and 5m periods (similar to the loadaverage). [hannes@cmpxchg.org: doc fixlet, per Randy] Link: http://lkml.kernel.org/r/20180828205625.GA14030@cmpxchg.org [hannes@cmpxchg.org: code optimization] Link: http://lkml.kernel.org/r/20180907175015.GA8479@cmpxchg.org [hannes@cmpxchg.org: rename psi_clock() to psi_update_work(), per Peter] Link: http://lkml.kernel.org/r/20180907145404.GB11088@cmpxchg.org [hannes@cmpxchg.org: fix build] Link: http://lkml.kernel.org/r/20180913014222.GA2370@cmpxchg.org Link: http://lkml.kernel.org/r/20180828172258.3185-9-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Daniel Drake <drake@endlessm.com> Tested-by: Suren Baghdasaryan <surenb@google.com> Cc: Christopher Lameter <cl@linux.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Johannes Weiner <jweiner@fb.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Enderborg <peter.enderborg@sony.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: Vinayak Menon <vinmenon@codeaurora.org> Cc: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
-rw-r--r--mm/vmscan.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 87e9fef341d2..8ea87586925e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -49,6 +49,7 @@
#include <linux/prefetch.h>
#include <linux/printk.h>
#include <linux/dax.h>
+#include <linux/psi.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
@@ -3305,6 +3306,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
{
struct zonelist *zonelist;
unsigned long nr_reclaimed;
+ unsigned long pflags;
int nid;
unsigned int noreclaim_flag;
struct scan_control sc = {
@@ -3333,9 +3335,13 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
sc.gfp_mask,
sc.reclaim_idx);
+ psi_memstall_enter(&pflags);
noreclaim_flag = memalloc_noreclaim_save();
+
nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
+
memalloc_noreclaim_restore(noreclaim_flag);
+ psi_memstall_leave(&pflags);
trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
@@ -3500,6 +3506,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
int i;
unsigned long nr_soft_reclaimed;
unsigned long nr_soft_scanned;
+ unsigned long pflags;
struct zone *zone;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
@@ -3510,6 +3517,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
.may_swap = 1,
};
+ psi_memstall_enter(&pflags);
__fs_reclaim_acquire();
count_vm_event(PAGEOUTRUN);
@@ -3611,6 +3619,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
out:
snapshot_refaults(NULL, pgdat);
__fs_reclaim_release();
+ psi_memstall_leave(&pflags);
/*
* Return the order kswapd stopped reclaiming at as
* prepare_kswapd_sleep() takes it into account. If another caller