Messages in this thread | | | Subject | Re: [PATCH v3 09/17] mm, compaction: make whole_zone flag ignore cached scanner positions | From | Vlastimil Babka <> | Date | Mon, 18 Jul 2016 11:12:51 +0200 |
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On 07/06/2016 07:09 AM, Joonsoo Kim wrote: > On Fri, Jun 24, 2016 at 11:54:29AM +0200, Vlastimil Babka wrote: >> A recent patch has added whole_zone flag that compaction sets when scanning >> starts from the zone boundary, in order to report that zone has been fully >> scanned in one attempt. For allocations that want to try really hard or cannot >> fail, we will want to introduce a mode where scanning whole zone is guaranteed >> regardless of the cached positions. >> >> This patch reuses the whole_zone flag in a way that if it's already passed true >> to compaction, the cached scanner positions are ignored. Employing this flag > > Okay. But, please don't reset cached scanner position even if whole_zone > flag is set. Just set cc->migrate_pfn and free_pfn, appropriately. With
Won't that result in confusion on cached position updates during compaction where it checks the previous cached position? I wonder what kinds of corner cases it can bring...
> your following patches, whole_zone could be set without any compaction > try
I don't understand what you mean here? Even after whole series, whole_zone is only checked, and positions thus reset, after passing the compaction_suitable() call from compact_zone(). So at that point we can say that compaction is being actually tried and it's not a drive-by reset?
Thanks
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