Pavel Machek wrote: > On Wed 2009-12-02 22:25:16, Mel Gorman wrote: > >> On Wed, Dec 02, 2009 at 11:15:24PM +0100, Pavel Machek wrote: >> >>> On Wed 2009-12-02 22:07:18, Mel Gorman wrote: >>> >>>> On Wed, Dec 02, 2009 at 10:11:07PM +0100, Pavel Machek wrote: >>>> >>>>> On Wed 2009-12-02 14:28:12, Alan Jenkins wrote: >>>>> >>>>>> The original in-kernel suspend (swsusp) frees the in-memory hibernation >>>>>> image before powering off the machine. s2disk doesn't, so there is >>>>>> _much_ less free memory when it tries to power off. >>>>>> >>>>>> This is a gratuitous difference. The userspace suspend interface >>>>>> /dev/snapshot only allows the hibernation image to be read once. >>>>>> Once the s2disk program has read the last page, we can free the entire >>>>>> image. >>>>>> >>>>>> This avoids a hang after writing the hibernation image which was >>>>>> triggered by commit 5f8dcc21211a3d4e3a7a5ca366b469fb88117f61 >>>>>> "page-allocator: split per-cpu list into one-list-per-migrate-type": >>>>>> >>>>> Yes, you work around page-allocator hang. But is it right thing to do? >>>>> >>>>> >>>> What's wrong with it? The hang is likely because the allocator has no >>>> memory to work with. The patch in question makes small changes to the >>>> amount of available memory but it shouldn't matter on uni-core. Some >>>> structures are slightly larger but it's extremely borderline. I'm at a >>>> loss to explain actually why it makes a difference untill things were >>>> extremely borderline to begin with. >>>> >>> We reserve 4MB, for such purposes, and we already wrote image to disk >>> with such constrains, so memory should not be _too_ tight. >>> >>> Can you try increasing PAGES_FOR_IO to 8MB or something like that? >>> >>> >> What's wrong with just freeing the memory that is no longer required? >> > > Nothing. But 4MB was enough to power down before, it is not enough > now, and I'd like to understand why. > Pavel > Here's a new datum: Applying this patch has left a less frequent hang. So far it has happened twice. (Once playing last night, and once today testing hibernation with KMS enabled). This hang happens at a different point. It happens _before_ writing out the hibernation image. That is, I don't see the textual progress bar, and if I force a power-cycle then it doesn't resume (and complains about uncleanly unmounted filesystems). Here is the backtrace: [top of screen] s2disk D c1c05580 0 5988 5809 0x00000000 ... Call Trace: ... ? wait_for_common ? default_wake_function ? kthread_create ? worker_thread ? create_workqueue_thread ? worker_thread ? __create_workqueue_thread ? stop_machine_create ? disable_nonboot_cpus ? hibernation_snapshot ? snapshot_ioctl ... ? sys_ioctl It looks like hibernation_snapshot() calls disable_nonboot_cpus() _before_ we allocate the hibernation image. (I.e. before swsusp_arch_suspend(), which calls swsusp_save()). So I think Pavel's right, we still need to work out what's happening here. Regards Alan _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
