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Date: Thu, 23 Jan 2014 14:05:58 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To: Len Brown <lenb@...nel.org>
CC: rjw@...ysocki.net, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>
Subject: Re: [PATCH v3] suspend: make sync() on suspend-to-RAM optional
On 01/23/2014 01:40 PM, Len Brown wrote:
> From: Len Brown <len.brown@...el.com>
>
> Linux suspend-to-RAM was unreliable when first developed,
> and so sys_sync() was invoked inside the kernel at the
> start of every suspend flow.
>
> Today, many devices invoke suspend with
> high reliability and high frequency.
> They may not want to be forced to pay
> the performance cost of sync() on every suspend.
>
> So here we make the file system sync() optional.
> De-select CONFIG_SUSPEND_FS_SYNC to delete the call.
> Keep CONFIG_SUSPEND_FS_SYNC keept the call, and also
> includes the new sysfs attribte,
> /sys/power/suspend_fs_sync
> which can be cleared to disable the file-system sync.
>
> As we have had this call for a long time,
> the default remains to keep the call, and to
> invoke it on every suspend.
>
> Signed-off-by: Len Brown <len.brown@...el.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Regards,
Srivatsa S. Bhat
> ---
> kernel/power/Kconfig | 11 +++++++++++
> kernel/power/main.c | 33 +++++++++++++++++++++++++++++++++
> kernel/power/power.h | 1 +
> kernel/power/suspend.c | 10 +++++++---
> 4 files changed, 52 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 2fac9cc..244c2d9 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -102,6 +102,17 @@ config PM_SLEEP_SMP
> depends on PM_SLEEP
> select HOTPLUG_CPU
>
> +config SUSPEND_FS_SYNC
> + bool "Suspend to RAM includes file-system sync()"
> + default y
> + depends on SUSPEND
> + ---help---
> + Include a file system sync() at the start of every suspend to RAM flow.
> + Disable this option to exclude that capability.
> +
> + If included, the sync can still be skipped
> + by clearing /sys/power/suspend_fs_sync.
> +
> config PM_AUTOSLEEP
> bool "Opportunistic sleep"
> depends on PM_SLEEP
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index 1d1bf63..bce7807 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -71,6 +71,36 @@ static ssize_t pm_async_store(struct kobject *kobj, struct kobj_attribute *attr,
>
> power_attr(pm_async);
>
> +#ifdef CONFIG_SUSPEND_FS_SYNC
> +
> +/* If set, sync file systems at start of suspend flow */
> +int suspend_fs_sync_enabled = 1;
> +
> +static ssize_t suspend_fs_sync_show(struct kobject *kobj, struct kobj_attribute *attr,
> + char *buf)
> +{
> + return sprintf(buf, "%d\n", suspend_fs_sync_enabled);
> +}
> +
> +static ssize_t suspend_fs_sync_store(struct kobject *kobj, struct kobj_attribute *attr,
> + const char *buf, size_t n)
> +{
> + unsigned long val;
> +
> + if (kstrtoul(buf, 10, &val))
> + return -EINVAL;
> +
> + if (val > 1)
> + return -EINVAL;
> +
> + suspend_fs_sync_enabled = val;
> + return n;
> +}
> +
> +power_attr(suspend_fs_sync);
> +
> +#endif /* CONFIG_SUSPEND_FS_SYNC */
> +
> #ifdef CONFIG_PM_DEBUG
> int pm_test_level = TEST_NONE;
>
> @@ -592,6 +622,9 @@ static struct attribute * g[] = {
> #ifdef CONFIG_PM_SLEEP
> &pm_async_attr.attr,
> &wakeup_count_attr.attr,
> +#ifdef CONFIG_SUSPEND_FS_SYNC
> + &suspend_fs_sync_attr.attr,
> +#endif
> #ifdef CONFIG_PM_AUTOSLEEP
> &autosleep_attr.attr,
> #endif
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 7d4b7ff..3d86f09 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -200,6 +200,7 @@ static inline void suspend_test_finish(const char *label) {}
> #ifdef CONFIG_PM_SLEEP
> /* kernel/power/main.c */
> extern int pm_notifier_call_chain(unsigned long val);
> +extern int suspend_fs_sync_enabled;
> #endif
>
> #ifdef CONFIG_HIGHMEM
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index 62ee437..e7eb2ba 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -333,9 +333,13 @@ static int enter_state(suspend_state_t state)
> if (state == PM_SUSPEND_FREEZE)
> freeze_begin();
>
> - printk(KERN_INFO "PM: Syncing filesystems ... ");
> - sys_sync();
> - printk("done.\n");
> +#ifdef CONFIG_SUSPEND_FS_SYNC
> + if (suspend_fs_sync_enabled) {
> + printk(KERN_INFO "PM: Syncing filesystems ... ");
> + sys_sync();
> + printk("done.\n");
> + }
> +#endif /* CONFIG_SUSPEND_FS_SYNC */
>
> pr_debug("PM: Preparing system for %s sleep\n", pm_states[state]);
> error = suspend_prepare(state);
>
--
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