| Message ID | 20201030183809.3616803-1-zi.yan@sent.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3,1/2] mm/compaction: count pages and stop correctly during page isolation. | expand |
On 10/30/20 7:38 PM, Zi Yan wrote: > From: Zi Yan <ziy@nvidia.com> > > In isolate_migratepages_block, when cc->alloc_contig is true, we are > able to isolate compound pages, nr_migratepages and nr_isolated did not > count compound pages correctly, causing us to isolate more pages than we > thought. Count compound pages as the number of base pages they contain. > Otherwise, we might be trapped in too_many_isolated while loop, > since the actual isolated pages can go up to > COMPACT_CLUSTER_MAX*512=16384, where COMPACT_CLUSTER_MAX is 32, > since we stop isolation after cc->nr_migratepages reaches to > COMPACT_CLUSTER_MAX. > > In addition, after we fix the issue above, cc->nr_migratepages could > never be equal to COMPACT_CLUSTER_MAX if compound pages are isolated, > thus page isolation could not stop as we intended. Change the isolation > stop condition to >=. > > The issue can be triggered as follows: > In a system with 16GB memory and an 8GB CMA region reserved by > hugetlb_cma, if we first allocate 10GB THPs and mlock them > (so some THPs are allocated in the CMA region and mlocked), reserving > 6 1GB hugetlb pages via > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages will get stuck > (looping in too_many_isolated function) until we kill either task. > With the patch applied, oom will kill the application with 10GB THPs and > let hugetlb page reservation finish. > > Fixes: 1da2f328fa64 (“mm,thp,compaction,cma: allow THP migration for CMA allocations”) > Signed-off-by: Zi Yan <ziy@nvidia.com> > Reviewed-by: Yang Shi <shy828301@gmail.com> > Cc: <stable@vger.kernel.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > mm/compaction.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index ee1f8439369e..3e834ac402f1 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -1012,8 +1012,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, > > isolate_success: > list_add(&page->lru, &cc->migratepages); > - cc->nr_migratepages++; > - nr_isolated++; > + cc->nr_migratepages += compound_nr(page); > + nr_isolated += compound_nr(page); > > /* > * Avoid isolating too much unless this block is being > @@ -1021,7 +1021,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, > * or a lock is contended. For contention, isolate quickly to > * potentially remove one source of contention. > */ > - if (cc->nr_migratepages == COMPACT_CLUSTER_MAX && > + if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX && > !cc->rescan && !cc->contended) { > ++low_pfn; > break; > @@ -1132,7 +1132,7 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, > if (!pfn) > break; > > - if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) > + if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX) > break; > } > >
diff --git a/mm/compaction.c b/mm/compaction.c index ee1f8439369e..3e834ac402f1 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1012,8 +1012,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, isolate_success: list_add(&page->lru, &cc->migratepages); - cc->nr_migratepages++; - nr_isolated++; + cc->nr_migratepages += compound_nr(page); + nr_isolated += compound_nr(page); /* * Avoid isolating too much unless this block is being @@ -1021,7 +1021,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, * or a lock is contended. For contention, isolate quickly to * potentially remove one source of contention. */ - if (cc->nr_migratepages == COMPACT_CLUSTER_MAX && + if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX && !cc->rescan && !cc->contended) { ++low_pfn; break; @@ -1132,7 +1132,7 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, if (!pfn) break; - if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) + if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX) break; }