The patch titled
Subject: psi-pressure-stall-information-for-cpu-memory-and-io-fix-2
has been added to the -mm tree. Its filename is
psi-pressure-stall-information-for-cpu-memory-and-io-fix-2.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/psi-pressure-stall-information-for-cpu-memory-and-io-fix-2.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/psi-pressure-stall-information-for-cpu-memory-and-io-fix-2.patch
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------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: psi-pressure-stall-information-for-cpu-memory-and-io-fix-2
Code optimization.
Still pretty readable, and generates compact code inside the now single
retry section:
ffffffff81ed464f: 44 89 ff mov %r15d,%edi
ffffffff81ed4652: e8 00 00 00 00 callq ffffffff81ed4657 <update_stats+0xca>
ffffffff81ed4653: R_X86_64_PLT32 sched_clock_cpu-0x4
memcpy(times, groupc->times, sizeof(groupc->times));
ffffffff81ed4657: 49 8b 14 24 mov (%r12),%rdx
state_start = groupc->state_start;
ffffffff81ed465b: 48 8b 4b 50 mov 0x50(%rbx),%rcx
memcpy(times, groupc->times, sizeof(groupc->times));
ffffffff81ed465f: 48 89 54 24 30 mov %rdx,0x30(%rsp)
ffffffff81ed4664: 49 8b 54 24 08 mov 0x8(%r12),%rdx
ffffffff81ed4669: 48 89 54 24 38 mov %rdx,0x38(%rsp)
ffffffff81ed466e: 49 8b 54 24 10 mov 0x10(%r12),%rdx
ffffffff81ed4673: 48 89 54 24 40 mov %rdx,0x40(%rsp)
memcpy(tasks, groupc->tasks, sizeof(groupc->tasks));
ffffffff81ed4678: 49 8b 55 00 mov 0x0(%r13),%rdx
ffffffff81ed467c: 48 89 54 24 24 mov %rdx,0x24(%rsp)
ffffffff81ed4681: 41 8b 55 08 mov 0x8(%r13),%edx
ffffffff81ed4685: 89 54 24 2c mov %edx,0x2c(%rsp)
Link: http://lkml.kernel.org/r/20180907175015.GA8479@xxxxxxxxxxx
Cc: Christopher Lameter <cl@xxxxxxxxx>
Cc: Daniel Drake <drake@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Johannes Weiner <jweiner@xxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Enderborg <peter.enderborg@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@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>
---
kernel/sched/psi.c | 43 +++++++++++++++++++++++++------------------
1 file changed, 25 insertions(+), 18 deletions(-)
--- a/kernel/sched/psi.c~psi-pressure-stall-information-for-cpu-memory-and-io-fix-2
+++ a/kernel/sched/psi.c
@@ -197,17 +197,26 @@ static bool test_state(unsigned int *tas
}
}
-static u32 get_recent_time(struct psi_group *group, int cpu,
- enum psi_states state)
+static void get_recent_times(struct psi_group *group, int cpu, u32 *times)
{
struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
+ unsigned int tasks[NR_PSI_TASK_COUNTS];
+ u64 now, state_start;
unsigned int seq;
- u32 time, delta;
+ int s;
+ /* Snapshot a coherent view of the CPU state */
do {
seq = read_seqcount_begin(&groupc->seq);
+ now = cpu_clock(cpu);
+ memcpy(times, groupc->times, sizeof(groupc->times));
+ memcpy(tasks, groupc->tasks, sizeof(groupc->tasks));
+ state_start = groupc->state_start;
+ } while (read_seqcount_retry(&groupc->seq, seq));
- time = groupc->times[state];
+ /* Calculate state time deltas against the previous snapshot */
+ for (s = 0; s < NR_PSI_STATES; s++) {
+ u32 delta;
/*
* In addition to already concluded states, we also
* incorporate currently active states on the CPU,
@@ -217,14 +226,14 @@ static u32 get_recent_time(struct psi_gr
* (u32) and our reported pressure close to what's
* actually happening.
*/
- if (test_state(groupc->tasks, state))
- time += cpu_clock(cpu) - groupc->state_start;
- } while (read_seqcount_retry(&groupc->seq, seq));
+ if (test_state(tasks, s))
+ times[s] += now - state_start;
- delta = time - groupc->times_prev[state];
- groupc->times_prev[state] = time;
+ delta = times[s] - groupc->times_prev[s];
+ groupc->times_prev[s] = times[s];
- return delta;
+ times[s] = delta;
+ }
}
static void calc_avgs(unsigned long avg[3], int missed_periods,
@@ -267,18 +276,16 @@ static bool update_stats(struct psi_grou
* loading, or even entirely idle CPUs.
*/
for_each_possible_cpu(cpu) {
+ u32 times[NR_PSI_STATES];
u32 nonidle;
- nonidle = get_recent_time(group, cpu, PSI_NONIDLE);
- nonidle = nsecs_to_jiffies(nonidle);
- nonidle_total += nonidle;
+ get_recent_times(group, cpu, times);
- for (s = 0; s < PSI_NONIDLE; s++) {
- u32 delta;
+ nonidle = nsecs_to_jiffies(times[PSI_NONIDLE]);
+ nonidle_total += nonidle;
- delta = get_recent_time(group, cpu, s);
- deltas[s] += (u64)delta * nonidle;
- }
+ for (s = 0; s < PSI_NONIDLE; s++)
+ deltas[s] += (u64)times[s] * nonidle;
}
/*
_
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-pressure-stall-information-for-cpu-memory-and-io-fix.patch
psi-pressure-stall-information-for-cpu-memory-and-io-fix-2.patch
psi-pressure-stall-information-for-cpu-memory-and-io-fix-3.patch
psi-cgroup-support.patch
