On Thu 15-11-18 16:07:16, Andrew Morton wrote:
> On Wed, 7 Nov 2018 11:18:30 +0100 Michal Hocko <mho...@kernel.org> wrote:
>
> > From: Michal Hocko <mho...@suse.com>
> >
> > There is only very limited information printed when the memory offlining
> > fails:
> > [ 1984.506184] rac1 kernel: memory offlining [mem
> > 0x82600000000-0x8267fffffff] failed due to signal backoff
> >
> > This tells us that the failure is triggered by the userspace
> > intervention but it doesn't tell us much more about the underlying
> > reason. It might be that the page migration failes repeatedly and the
> > userspace timeout expires and send a signal or it might be some of the
> > earlier steps (isolation, memory notifier) takes too long.
> >
> > If the migration failes then it would be really helpful to see which
> > page that and its state. The same applies to the isolation phase. If we
> > fail to isolate a page from the allocator then knowing the state of the
> > page would be helpful as well.
> >
> > Dump the page state that fails to get isolated or migrated. This will
> > tell us more about the failure and what to focus on during debugging.
> >
> > ...
> >
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -1388,10 +1388,8 @@ do_migrate_range(unsigned long start_pfn, unsigned
> > long end_pfn)
> > page_is_file_cache(page));
> >
> > } else {
> > -#ifdef CONFIG_DEBUG_VM
> > - pr_alert("failed to isolate pfn %lx\n", pfn);
> > + pr_warn("failed to isolate pfn %lx\n", pfn);
> > dump_page(page, "isolation failed");
> > -#endif
> > put_page(page);
> > /* Because we don't have big zone->lock. we should
> > check this again here. */
> > @@ -1411,8 +1409,14 @@ do_migrate_range(unsigned long start_pfn, unsigned
> > long end_pfn)
> > /* Allocate a new page from the nearest neighbor node */
> > ret = migrate_pages(&source, new_node_page, NULL, 0,
> > MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
> > - if (ret)
> > + if (ret) {
> > + list_for_each_entry(page, &source, lru) {
> > + pr_warn("migrating pfn %lx failed ",
> > + page_to_pfn(page), ret);
> > + dump_page(page, NULL);
> > + }
>
> ./include/linux/kern_levels.h:5:18: warning: too many arguments for format
> [-Wformat-extra-args]
> #define KERN_SOH "\001" /* ASCII Start Of Header */
> ^
> ./include/linux/kern_levels.h:12:22: note: in expansion of macro ‘KERN_SOH’
> #define KERN_WARNING KERN_SOH "4" /* warning conditions */
> ^~~~~~~~
> ./include/linux/printk.h:310:9: note: in expansion of macro ‘KERN_WARNING’
> printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
> ^~~~~~~~~~~~
> ./include/linux/printk.h:311:17: note: in expansion of macro ‘pr_warning’
> #define pr_warn pr_warning
> ^~~~~~~~~~
> mm/memory_hotplug.c:1414:5: note: in expansion of macro ‘pr_warn’
> pr_warn("migrating pfn %lx failed ",
> ^~~~~~~
yeah, 0day already complained and I've posted a follow up fix
http://lkml.kernel.org/r/20181108081231.gn27...@dhcp22.suse.cz
Let me post a version 2 with all the fixups.
Thanks!
> ---
> a/mm/memory_hotplug.c~mm-memory_hotplug-be-more-verbose-for-memory-offline-failures-fix
> +++ a/mm/memory_hotplug.c
> @@ -1411,7 +1411,7 @@ do_migrate_range(unsigned long start_pfn
> MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
> if (ret) {
> list_for_each_entry(page, &source, lru) {
> - pr_warn("migrating pfn %lx failed ",
> + pr_warn("migrating pfn %lx failed: %d",
> page_to_pfn(page), ret);
> dump_page(page, NULL);
> }
>
--
Michal Hocko
SUSE Labs
