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    SubjectRe: [PATCH 1/3] perf: add calls to suspend trace point
    Date
    On Wednesday, January 05, 2011, Jean Pihet wrote:
    > On Wed, Jan 5, 2011 at 12:01 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    > > On Tuesday, January 04, 2011, Jean Pihet wrote:
    > >> Hi,
    > >>
    > >> On Tue, Jan 4, 2011 at 12:29 PM, Pavel Machek <pavel@ucw.cz> wrote:
    > >> > Hi!
    > >> >
    > >> >> Uses the machine_suspend trace point, called from the
    > >> >> generic kernel suspend_enter function.
    > >> >>
    > >> >> Signed-off-by: Jean Pihet <j-pihet@ti.com>
    > >> >> CC: Thomas Renninger <trenn@suse.de>
    > >> >> ---
    > >> >> kernel/power/suspend.c | 3 +++
    > >> >> 1 files changed, 3 insertions(+), 0 deletions(-)
    > >> >>
    > >> >> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
    > >> >> index ecf7705..0650596 100644
    > >> >> --- a/kernel/power/suspend.c
    > >> >> +++ b/kernel/power/suspend.c
    > >> >> @@ -22,6 +22,7 @@
    > >> >> #include <linux/mm.h>
    > >> >> #include <linux/slab.h>
    > >> >> #include <linux/suspend.h>
    > >> >> +#include <trace/events/power.h>
    > >> >>
    > >> >> #include "power.h"
    > >> >>
    > >> >> @@ -164,7 +165,9 @@ static int suspend_enter(suspend_state_t state)
    > >> >> error = sysdev_suspend(PMSG_SUSPEND);
    > >> >> if (!error) {
    > >> >> if (!suspend_test(TEST_CORE) && pm_check_wakeup_events()) {
    > >> >> + trace_machine_suspend(state);
    > >> >> error = suspend_ops->enter(state);
    > >> >> + trace_machine_suspend(PWR_EVENT_EXIT);
    > >> >> events_check_enabled = false;
    > >> >> }
    > >> >> sysdev_resume();
    > >> >
    > >> > Ok... why this place?
    > >> This trace has been placed here because it traces the machine low
    > >> level mode enter.
    > >>
    > >> > I mean, perhaps suspend time should include
    > >> > device suspend?
    > >> That makes sense. We have a few options here:
    > >> 1) keep the traces as proposed to trace the low level machine code only,
    > >> 2) move the traces to the entry and exit of suspend_enter so that it
    > >> includes the prepare and late_prepare (+ the associated wake-up)
    > >> callbacks as well,
    > >> 3) move the traces to suspend_devices_and_enter so that it includes 2)
    > >> and the handling of the console and the devices,
    > >> 4) move the traces to enter_state do that it includes 3), the call to
    > >> sys_sync and the user space freeze.
    > >>
    > >> Note that the the SNAPSHOT_2RAM ioctl code also calls
    > >> suspend_devices_and_enter, so if only 4) is used no trace will be
    > >> generated in that case.
    > >>
    > >> I am in favor of 3) of 4).
    > >> What do you think?
    > >
    > > Why don't we keep the tracepoints as proposed _and_ add two additional
    > > tracepoints around device suspend-resume?
    > I like the idea but that requires to extend the current API with
    > additional suspend tracepoints or device state change tracepoints.
    > That can be done once the current API is firmly in place.
    > Today the only trace API for suspend is machine_suspend(unsigned int
    > state), so I think the best option is 3) here above.
    >
    > Unless there is an objection I am pushing 3) asap.

    Fine by me.

    Thanks,
    Rafael


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