From: Michal Hocko <mhocko@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>,
David Hildenbrand <david@redhat.com>,
Oscar Salvador <osalvador@suse.de>
Subject: [PATCH 2/3] mm, memory_hotplug: deobfuscate migration part of offlining
Date: Tue, 11 Dec 2018 15:27:40 +0100 [thread overview]
Message-ID: <20181211142741.2607-3-mhocko@kernel.org> (raw)
In-Reply-To: <20181211142741.2607-1-mhocko@kernel.org>
From: Michal Hocko <mhocko@suse.com>
Memory migration might fail during offlining and we keep retrying in
that case. This is currently obfuscate by goto retry loop. The code
is hard to follow and as a result it is even suboptimal becase each
retry round scans the full range from start_pfn even though we have
successfully scanned/migrated [start_pfn, pfn] range already. This
is all only because check_pages_isolated failure has to rescan the full
range again.
De-obfuscate the migration retry loop by promoting it to a real for
loop. In fact remove the goto altogether by making it a proper double
loop (yeah, gotos are nasty in this specific case). In the end we
will get a slightly more optimal code which is better readable.
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
mm/memory_hotplug.c | 58 ++++++++++++++++++++++-----------------------
1 file changed, 29 insertions(+), 29 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6263c8cd4491..c6c42a7425e5 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1591,38 +1591,38 @@ static int __ref __offline_pages(unsigned long start_pfn,
goto failed_removal_isolated;
}
- pfn = start_pfn;
-repeat:
- /* start memory hot removal */
- ret = -EINTR;
- if (signal_pending(current)) {
- reason = "signal backoff";
- goto failed_removal_isolated;
- }
+ do {
+ for (pfn = start_pfn; pfn;) {
+ if (signal_pending(current)) {
+ ret = -EINTR;
+ reason = "signal backoff";
+ goto failed_removal_isolated;
+ }
- cond_resched();
- lru_add_drain_all();
- drain_all_pages(zone);
+ 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;
- }
+ pfn = scan_movable_pages(pfn, end_pfn);
+ if (pfn) {
+ /* TODO fatal migration failures should bail out */
+ do_migrate_range(pfn, end_pfn);
+ }
+ }
+
+ /*
+ * dissolve free hugepages in the memory block before doing offlining
+ * actually in order to make hugetlbfs's object counting consistent.
+ */
+ ret = dissolve_free_huge_pages(start_pfn, end_pfn);
+ if (ret) {
+ reason = "failure to dissolve huge pages";
+ goto failed_removal_isolated;
+ }
+ /* check again */
+ offlined_pages = check_pages_isolated(start_pfn, end_pfn);
+ } while (offlined_pages < 0);
- /*
- * dissolve free hugepages in the memory block before doing offlining
- * actually in order to make hugetlbfs's object counting consistent.
- */
- ret = dissolve_free_huge_pages(start_pfn, end_pfn);
- if (ret) {
- reason = "failure to dissolve huge pages";
- goto failed_removal_isolated;
- }
- /* check again */
- offlined_pages = check_pages_isolated(start_pfn, end_pfn);
- if (offlined_pages < 0)
- goto repeat;
pr_info("Offlined Pages %ld\n", offlined_pages);
/* Ok, all of our target is isolated.
We cannot do rollback at this point. */
--
2.19.2
next prev parent reply other threads:[~2018-12-11 14:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-11 14:27 [PATCH 0/3] few memory offlining enhancements Michal Hocko
2018-12-11 14:27 ` [PATCH 1/3] mm, memory_hotplug: try to migrate full pfn range Michal Hocko
2018-12-12 1:12 ` Wei Yang
2018-12-11 14:27 ` Michal Hocko [this message]
2018-12-11 14:27 ` [PATCH 3/3] mm, fault_around: do not take a reference to a locked page Michal Hocko
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