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SubjectRe: Performance/resume issues on Toshiba NB305
Would be helpful to Cc the people that may help you.


On Fri, Feb 25, 2011 at 10:42:39AM -0600, Seth Forshee wrote:
> I've been looking into a couple of problems with this machine that have
> me a bit stumped at the moment. The two problems may or may not be
> related, so I'm including details about both issues below. If anyone has
> any ideas, I'd love to hear them. Note that these are not recent
> regressions; they've been around since at least 2.6.32.
>
> The CPU in this machine is an Atom N450.
>
> When booted normally the performance on this machine is very poor, but
> when booted with any of nohz=off, nolapic, or nohpet it improves
> significantly. The performance also improves if I use the patch below to
> force the hpet to remain in periodic mode (with hpet=periodic on the
> command line).
>
> One other thing I noticed when I had added some logging related to hpet
> rearming is 3-5 second periods of no log activity occurring fairly
> frequently, whereas such inactive periods are infrequent when
> performance is good and are also infrequent on another machine with very
> similar hardware and no performance issues.
>
> The machine also hangs for 5 minutes during resume, unless booted with
> both nohz=off and highres=off, or with hpet=periodic using the patch
> below. I've traced this down to hanging in an SMI handler during the
> ACPI _WAK method execution. The 5 minutes corresponds to how long it
> takes for the low 32 bits of the hpet to wrap in this machine, and since
> the options that eliminate the hang result in the hpet being in periodic
> mode during _WAK method execution I suspect that the SMI handler is
> hanging until a timer interrupt happens.
>
> One possible explanation here is that the performance problems are also
> related to hangs in SMI handlers until there's a timer interrupt,
> although I don't know how that explains why some of the command line
> options eliminate the performance issues.

Sounds like a buggy BIOS to me. Is there upgrades available for this
box?

-- Steve

>
> Note also that I've already looked into the triggering for IRQ0, and it
> seems to be correct.
>
> Thanks,
> Seth
>
>
> diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
> index 4ff5968..ab10012 100644
> --- a/arch/x86/kernel/hpet.c
> +++ b/arch/x86/kernel/hpet.c
> @@ -87,6 +87,7 @@ static inline void hpet_clear_mapping(void)
> static int boot_hpet_disable;
> int hpet_force_user;
> static int hpet_verbose;
> +static int hpet_oneshot_disable;
>
> static int __init hpet_setup(char *str)
> {
> @@ -97,6 +98,8 @@ static int __init hpet_setup(char *str)
> hpet_force_user = 1;
> if (!strncmp("verbose", str, 7))
> hpet_verbose = 1;
> + if (!strncmp("periodic", str, 8))
> + hpet_oneshot_disable = 1;
> }
> return 1;
> }
> @@ -306,6 +309,10 @@ static void hpet_legacy_clockevent_register(void)
> hpet_clockevent.min_delta_ns = clockevent_delta2ns(HPET_MIN_PROG_DELTA,
> &hpet_clockevent);
>
> + /* Disable one-shot mode if requested */
> + if (hpet_oneshot_disable)
> + hpet_clockevent.features &= ~CLOCK_EVT_FEAT_ONESHOT;
> +
> /*
> * Start hpet with the boot cpu mask and make it
> * global after the IO_APIC has been initialized.
> diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
> index 48b2761..8e84c11 100644
> --- a/kernel/time/tick-broadcast.c
> +++ b/kernel/time/tick-broadcast.c
> @@ -565,10 +565,15 @@ void tick_broadcast_switch_to_oneshot(void)
>
> raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
>
> - tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
> bc = tick_broadcast_device.evtdev;
> + if (bc && !(bc->features & CLOCK_EVT_FEAT_ONESHOT))
> + goto unlock;
> +
> + tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
> if (bc)
> tick_broadcast_setup_oneshot(bc);
> +
> +unlock:
> raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
> }
>


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