From: Chengming Zhou <zhouchengming@bytedance.com>
To: hannes@cmpxchg.org, surenb@google.com, mingo@redhat.com,
peterz@infradead.org, tj@kernel.org, corbet@lwn.net,
akpm@linux-foundation.org, rdunlap@infradead.org
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
songmuchun@bytedance.com, cgroups@vger.kernel.org,
Chengming Zhou <zhouchengming@bytedance.com>
Subject: [PATCH 2/9] sched/psi: optimize task switch inside shared cgroups again
Date: Thu, 21 Jul 2022 12:04:32 +0800 [thread overview]
Message-ID: <20220721040439.2651-3-zhouchengming@bytedance.com> (raw)
In-Reply-To: <20220721040439.2651-1-zhouchengming@bytedance.com>
commit 4117cebf1a9f ("psi: Optimize task switch inside shared cgroups")
defer prev task sleep handling to psi_task_switch(), so we don't need
to clear and set TSK_ONCPU state for common cgroups.
A
|
B
/ \
C D
/ \
prev next
After that commit psi_task_switch() do:
1. psi_group_change(next, .set=TSK_ONCPU) for D
2. psi_group_change(prev, .clear=TSK_ONCPU | TSK_RUNNING) for C
3. psi_group_change(prev, .clear=TSK_RUNNING) for B, A
But there is a limitation "prev->psi_flags == next->psi_flags" that
if not satisfied, will make this cgroups optimization unusable for both
sleep switch or running switch cases. For example:
prev->in_memstall != next->in_memstall when sleep switch:
1. psi_group_change(next, .set=TSK_ONCPU) for D, B, A
2. psi_group_change(prev, .clear=TSK_ONCPU | TSK_RUNNING) for C, B, A
prev->in_memstall != next->in_memstall when running switch:
1. psi_group_change(next, .set=TSK_ONCPU) for D, B, A
2. psi_group_change(prev, .clear=TSK_ONCPU) for C, B, A
The reason why this limitation exist is that we consider a group is
PSI_MEM_FULL if the CPU is actively reclaiming and nothing productive
could run even if it were runnable. So when CPU curr changed from prev
to next and their in_memstall status is different, we have to change
PSI_MEM_FULL status for their common cgroups.
This patch remove this limitation by making psi_group_change() change
PSI_MEM_FULL status depend on CPU curr->in_memstall status.
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
---
kernel/sched/psi.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index c8a4e644cd2c..e04041d8251b 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -823,8 +823,6 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
u64 now = cpu_clock(cpu);
if (next->pid) {
- bool identical_state;
-
psi_flags_change(next, 0, TSK_ONCPU);
/*
* When switching between tasks that have an identical
@@ -832,11 +830,9 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
* we reach the first common ancestor. Iterate @next's
* ancestors only until we encounter @prev's ONCPU.
*/
- identical_state = prev->psi_flags == next->psi_flags;
iter = NULL;
while ((group = iterate_groups(next, &iter))) {
- if (identical_state &&
- per_cpu_ptr(group->pcpu, cpu)->tasks[NR_ONCPU]) {
+ if (per_cpu_ptr(group->pcpu, cpu)->tasks[NR_ONCPU]) {
common = group;
break;
}
@@ -883,7 +879,7 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
* TSK_ONCPU is handled up to the common ancestor. If we're tasked
* with dequeuing too, finish that for the rest of the hierarchy.
*/
- if (sleep) {
+ if (sleep || unlikely(prev->in_memstall != next->in_memstall)) {
clear &= ~TSK_ONCPU;
for (; group; group = iterate_groups(prev, &iter))
psi_group_change(group, cpu, clear, set, now, true);
--
2.36.1
next prev parent reply other threads:[~2022-07-21 4:05 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-21 4:04 [PATCH 0/9] sched/psi: some optimization and extension Chengming Zhou
2022-07-21 4:04 ` [PATCH 1/9] sched/psi: fix periodic aggregation shut off Chengming Zhou
2022-07-25 15:34 ` Johannes Weiner
2022-07-25 15:39 ` Johannes Weiner
2022-07-26 13:28 ` Chengming Zhou
2022-07-21 4:04 ` Chengming Zhou [this message]
2022-07-21 4:04 ` [PATCH 3/9] sched/psi: move private helpers to sched/stats.h Chengming Zhou
2022-07-25 16:39 ` Johannes Weiner
2022-07-21 4:04 ` [PATCH 4/9] sched/psi: don't change task psi_flags when migrate CPU/group Chengming Zhou
2022-07-21 4:04 ` [PATCH 5/9] sched/psi: don't create cgroup PSI files when psi_disabled Chengming Zhou
2022-07-25 16:41 ` Johannes Weiner
2022-07-21 4:04 ` [PATCH 6/9] sched/psi: save percpu memory when !psi_cgroups_enabled Chengming Zhou
2022-07-25 16:47 ` Johannes Weiner
2022-07-21 4:04 ` [PATCH 7/9] sched/psi: cache parent psi_group to speed up groups iterate Chengming Zhou
2022-07-21 4:04 ` [PATCH 8/9] sched/psi: add kernel cmdline parameter psi_inner_cgroup Chengming Zhou
2022-07-25 16:52 ` Johannes Weiner
2022-07-26 13:38 ` [External] " Chengming Zhou
2022-07-26 17:54 ` Tejun Heo
2022-08-03 12:17 ` Chengming Zhou
2022-08-03 17:58 ` Tejun Heo
2022-08-03 19:22 ` Johannes Weiner
2022-08-03 19:48 ` Tejun Heo
2022-08-04 13:51 ` Chengming Zhou
2022-08-04 16:56 ` Johannes Weiner
2022-08-04 2:02 ` Chengming Zhou
2022-07-21 4:04 ` [PATCH 9/9] sched/psi: add PSI_IRQ to track IRQ/SOFTIRQ pressure Chengming Zhou
2022-07-21 10:00 ` kernel test robot
2022-07-21 22:10 ` kernel test robot
2022-07-22 3:30 ` Abel Wu
2022-07-22 6:13 ` Chengming Zhou
2022-07-22 7:14 ` Abel Wu
2022-07-22 7:33 ` Chengming Zhou
2022-07-25 18:26 ` Johannes Weiner
2022-07-26 13:55 ` [External] " Chengming Zhou
2022-07-27 11:28 ` Chengming Zhou
2022-07-27 13:00 ` Johannes Weiner
2022-07-27 15:09 ` Chengming Zhou
2022-07-27 16:07 ` Peter Zijlstra
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