From: John Allen <jallen@linux.ibm.com>
To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Cc: jallen@linux.ibm.com, kamezawa.hiroyu@jp.fujitsu.com,
n-horiguchi@ah.jp.nec.com, mgorman@suse.de, mhocko@suse.cz
Subject: Infinite looping observed in __offline_pages
Date: Wed, 25 Jul 2018 13:11:15 -0500 [thread overview]
Message-ID: <20180725181115.hmlyd3tmnu3mn3sf@p50.austin.ibm.com> (raw)
Hi All,
Under heavy stress and constant memory hot add/remove, I have observed
the following loop to occasionally loop infinitely:
mm/memory_hotplug.c:__offline_pages
repeat:
/* start memory hot removal */
ret = -EINTR;
if (signal_pending(current))
goto failed_removal;
cond_resched();
lru_add_drain_all();
drain_all_pages(zone);
pfn = scan_movable_pages(start_pfn, end_pfn);
if (pfn) { /* We have movable pages */
ret = do_migrate_range(pfn, end_pfn);
goto repeat;
}
What appears to be happening in this case is that do_migrate_range
returns a failure code which is being ignored. The failure is stemming
from migrate_pages returning "1" which I'm guessing is the result of us
hitting the following case:
mm/migrate.c: migrate_pages
default:
/*
* Permanent failure (-EBUSY, -ENOSYS, etc.):
* unlike -EAGAIN case, the failed page is
* removed from migration page list and not
* retried in the next outer loop.
*/
nr_failed++;
break;
}
Does a failure in do_migrate_range indicate that the range is
unmigratable and the loop in __offline_pages should terminate and goto
failed_removal? Or should we allow a certain number of retrys before we
give up on migrating the range?
This issue was observed on a ppc64le lpar on a 4.18-rc6 kernel.
-John
next reply other threads:[~2018-07-25 18:11 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-25 18:11 John Allen [this message]
2018-07-25 20:03 ` Infinite looping observed in __offline_pages Michal Hocko
2018-07-27 17:32 ` John Allen
2018-07-30 9:16 ` Michal Hocko
2018-08-01 11:09 ` Michael Ellerman
2018-08-01 11:20 ` Michal Hocko
2018-08-22 9:30 ` Aneesh Kumar K.V
2018-08-22 10:53 ` Michal Hocko
2018-08-22 18:58 ` Mike Kravetz
2018-08-23 3:01 ` Aneesh Kumar K.V
2018-08-23 7:25 ` Michal Hocko
2018-08-01 1:37 ` Rashmica
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