The patch titled
Subject: kernel/latencytop.c: remove unnecessary checks for latencytop_enabled
has been added to the -mm tree. Its filename is
kernel-latencytopc-remove-unnecessary-checks-for-latencytop_enabled.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kernel-latencytopc-remove-unnecessary-checks-for-latencytop_enabled.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kernel-latencytopc-remove-unnecessary-checks-for-latencytop_enabled.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** 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: Lin Feng <linf@xxxxxxxxxx>
Subject: kernel/latencytop.c: remove unnecessary checks for latencytop_enabled
1. In latencytop source codes, we only have such calling chain:
account_scheduler_latency(struct task_struct *task, int usecs, int inter)
{
if (unlikely(latencytop_enabled)) /* the outtermost check */
__account_scheduler_latency(task, usecs, inter);
}
__account_scheduler_latency
account_global_scheduler_latency
if (!latencytop_enabled)
So, the inner check for latencytop_enabled is not necessary at all.
2. In clear_all_latency_tracing and now is called
clear_tsk_latency_tracing the check for latencytop_enabled is redundant
and buggy to some extent.
We have no reason to refuse clearing the /proc/$pid/latency if
latencytop_enabled is set to 0, considering that if we use latencytop
manually by echo 0 > /proc/sys/kernel/latencytop, then we want to clear
/proc/$pid/latency and failed.
Also we don't have such check in brother function
clear_global_latency_tracing.
Notes: These changes are only visible to users who set
CONFIG_LATENCYTOP and won't change user tool latencytop's behavior.
Link: http://lkml.kernel.org/r/20190226114602.16902-2-linf@xxxxxxxxxx
Signed-off-by: Lin Feng <linf@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Fabian Frederick <fabf@xxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/latencytop.c | 6 ------
1 file changed, 6 deletions(-)
--- a/kernel/latencytop.c~kernel-latencytopc-remove-unnecessary-checks-for-latencytop_enabled
+++ a/kernel/latencytop.c
@@ -71,9 +71,6 @@ void clear_tsk_latency_tracing(struct ta
{
unsigned long flags;
- if (!latencytop_enabled)
- return;
-
raw_spin_lock_irqsave(&latency_lock, flags);
memset(&p->latency_record, 0, sizeof(p->latency_record));
p->latency_record_count = 0;
@@ -96,9 +93,6 @@ account_global_scheduler_latency(struct
int firstnonnull = MAXLR + 1;
int i;
- if (!latencytop_enabled)
- return;
-
/* skip kernel threads for now */
if (!tsk->mm)
return;
_
Patches currently in -mm which might be from linf@xxxxxxxxxx are
kernel-latencytopc-rename-clear_all_latency_tracing-to-clear_tsk_latency_tracing.patch
kernel-latencytopc-remove-unnecessary-checks-for-latencytop_enabled.patch
