Messages in this thread | | | Date | Tue, 04 Nov 2014 09:46:09 +0100 | From | Vlastimil Babka <> | Subject | Re: [PATCH v2 for v3.18] mm/compaction: skip the range until proper target pageblock is met |
| |
On 11/04/2014 03:37 AM, Joonsoo Kim wrote: > commit 7d49d8868336 ("mm, compaction: reduce zone checking frequency in > the migration scanner") makes side-effect that change iteration > range calculation. Before change, block_end_pfn is calculated using > start_pfn, but, now, blindly add pageblock_nr_pages to previous value. > > This cause the problem that isolation_start_pfn is larger than > block_end_pfn when we isolate the page with more than pageblock order. > In this case, isolation would be failed due to invalid range parameter. > > To prevent this, this patch recalculate the range to find valid target > pageblock. Without this patch, CMA with more than pageblock order always > fail, but, with this patch, it will succeed. > > Changes from v1: > recalculate the range rather than just skipping to find valid one. > add code comment. > > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
(nitpick below)
> --- > mm/compaction.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/compaction.c b/mm/compaction.c > index ec74cf0..4f0151c 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -479,6 +479,16 @@ isolate_freepages_range(struct compact_control *cc, > > block_end_pfn = min(block_end_pfn, end_pfn); > > + /* > + * pfn could pass the block_end_pfn if isolated freepage > + * is more than pageblock order. In this case, we adjust > + * scanning range to right one. > + */ > + if (pfn >= block_end_pfn) { > + block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); > + block_end_pfn = min(block_end_pfn, end_pfn); > + }
If you moved this up, there could be just one min(block_end_pfn, end_pfn) instance in the code. If the first min() makes block_end_pfn == end_pfn and pfn >= block_end_pfn, then pfn >= end_pfn and the loop would be terminated already (assuming this was why you left the first min() before the new check). But I don't mind if you leave it like this.
> + > if (!pageblock_pfn_to_page(pfn, block_end_pfn, cc->zone)) > break; > >
| |