| Message ID | 1367458508-9133-3-git-send-email-ccross@android.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Wed, May 01, 2013 at 06:35:00PM -0700, Colin Cross wrote: > Android goes through suspend/resume very often (every few seconds when > on a busy wifi network with the screen off), and a significant portion > of the energy used to go in and out of suspend is spent in the > freezer. If a task has called freezer_do_not_count(), don't bother > waking it up. If it happens to wake up later it will call > freezer_count() and immediately enter the refrigerator. > > Combined with patches to convert freezable helpers to use > freezer_do_not_count() and convert common sites where idle userspace > tasks are blocked to use the freezable helpers, this reduces the > time and energy required to suspend and resume. > > Signed-off-by: Colin Cross <ccross@android.com> > --- > v2: move check to freeze_task() > > kernel/freezer.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/kernel/freezer.c b/kernel/freezer.c > index c38893b..8b2afc1 100644 > --- a/kernel/freezer.c > +++ b/kernel/freezer.c > @@ -110,6 +110,18 @@ bool freeze_task(struct task_struct *p) > { > unsigned long flags; > > + /* > + * This check can race with freezer_do_not_count, but worst case that > + * will result in an extra wakeup being sent to the task. It does not > + * race with freezer_count(), the barriers in freezer_count() and > + * freezer_should_skip() ensure that either freezer_count() sees > + * freezing == true in try_to_freeze() and freezes, or > + * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task > + * normally. > + */ > + if (freezer_should_skip(p)) > + return false; Maybe a line or two explaining that this matters for power saving? Other than that, Acked-by: Tejun Heo <tj@kernel.org> Oleg, this looks correct to me. Can you please ack too? Thanks.
On Wed 2013-05-01 18:35:00, Colin Cross wrote: > Android goes through suspend/resume very often (every few seconds when > on a busy wifi network with the screen off), and a significant portion > of the energy used to go in and out of suspend is spent in the > freezer. If a task has called freezer_do_not_count(), don't bother > waking it up. If it happens to wake up later it will call > freezer_count() and immediately enter the refrigerator. > > Combined with patches to convert freezable helpers to use > freezer_do_not_count() and convert common sites where idle userspace > tasks are blocked to use the freezable helpers, this reduces the > time and energy required to suspend and resume. > > Signed-off-by: Colin Cross <ccross@android.com> Acked-by: Pavel Machek <pavel@ucw.cz>
diff --git a/kernel/freezer.c b/kernel/freezer.c index c38893b..8b2afc1 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -110,6 +110,18 @@ bool freeze_task(struct task_struct *p) { unsigned long flags; + /* + * This check can race with freezer_do_not_count, but worst case that + * will result in an extra wakeup being sent to the task. It does not + * race with freezer_count(), the barriers in freezer_count() and + * freezer_should_skip() ensure that either freezer_count() sees + * freezing == true in try_to_freeze() and freezes, or + * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task + * normally. + */ + if (freezer_should_skip(p)) + return false; + spin_lock_irqsave(&freezer_lock, flags); if (!freezing(p) || frozen(p)) { spin_unlock_irqrestore(&freezer_lock, flags);
Android goes through suspend/resume very often (every few seconds when on a busy wifi network with the screen off), and a significant portion of the energy used to go in and out of suspend is spent in the freezer. If a task has called freezer_do_not_count(), don't bother waking it up. If it happens to wake up later it will call freezer_count() and immediately enter the refrigerator. Combined with patches to convert freezable helpers to use freezer_do_not_count() and convert common sites where idle userspace tasks are blocked to use the freezable helpers, this reduces the time and energy required to suspend and resume. Signed-off-by: Colin Cross <ccross@android.com> --- v2: move check to freeze_task() kernel/freezer.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)