From: Zi Yan <ziy@nvidia.com>
To: Rik van Riel <riel@surriel.com>
Cc: <linux-kernel@vger.kernel.org>, <riel@fb.com>,
<kernel-team@fb.com>, <akpm@linux-foundation.org>,
<linux-mm@kvack.org>, <mhocko@kernel.org>, <vbabka@suse.cz>,
<mgorman@techsingularity.net>, <rientjes@google.com>,
<aarcange@redhat.com>
Subject: Re: [PATCH 2/2] mm,thp,compaction,cma: allow THP migration for CMA allocations
Date: Fri, 21 Feb 2020 17:31:05 -0500 [thread overview]
Message-ID: <FF5B51C0-8D6E-47AB-82C8-020D5C522502@nvidia.com> (raw)
In-Reply-To: <3289dc5e6c4c3174999598d8293adf8ed3e93b57.1582321645.git.riel@surriel.com>
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On 21 Feb 2020, at 16:53, Rik van Riel wrote:
> The code to implement THP migrations already exists, and the code
> for CMA to clear out a region of memory already exists.
>
> Only a few small tweaks are needed to allow CMA to move THP memory
> when attempting an allocation from alloc_contig_range.
>
> With these changes, migrating THPs from a CMA area works when
> allocating a 1GB hugepage from CMA memory.
>
> Signed-off-by: Rik van Riel <riel@surriel.com>
> ---
> mm/compaction.c | 16 +++++++++-------
> mm/page_alloc.c | 6 ++++--
> 2 files changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 672d3c78c6ab..f3e05c91df62 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -894,12 +894,12 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>
> /*
> * Regardless of being on LRU, compound pages such as THP and
> - * hugetlbfs are not to be compacted. We can potentially save
> - * a lot of iterations if we skip them at once. The check is
> - * racy, but we can consider only valid values and the only
> - * danger is skipping too much.
> + * hugetlbfs are not to be compacted most of the time. We can
> + * potentially save a lot of iterations if we skip them at
> + * once. The check is racy, but we can consider only valid
> + * values and the only danger is skipping too much.
> */
Maybe add “we do want to move them when allocating contiguous memory using CMA” to help
people understand the context of using cc->alloc_contig?
> - if (PageCompound(page)) {
> + if (PageCompound(page) && !cc->alloc_contig) {
> const unsigned int order = compound_order(page);
>
> if (likely(order < MAX_ORDER))
> @@ -969,7 +969,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> * and it's on LRU. It can only be a THP so the order
> * is safe to read and it's 0 for tail pages.
> */
> - if (unlikely(PageCompound(page))) {
> + if (unlikely(PageCompound(page) && !cc->alloc_contig)) {
> low_pfn += compound_nr(page) - 1;
> goto isolate_fail;
> }
> @@ -981,7 +981,9 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
> if (__isolate_lru_page(page, isolate_mode) != 0)
> goto isolate_fail;
>
> - VM_BUG_ON_PAGE(PageCompound(page), page);
> + /* The whole page is taken off the LRU; skip the tail pages. */
> + if (PageCompound(page))
> + low_pfn += compound_nr(page) - 1;
>
> /* Successfully isolated */
> del_page_from_lru_list(page, lruvec, page_lru(page));
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a36736812596..38c8ddfcecc8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8253,14 +8253,16 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>
> /*
> * Hugepages are not in LRU lists, but they're movable.
> + * THPs are on the LRU, but need to be counted as #small pages.
> * We need not scan over tail pages because we don't
> * handle each tail page individually in migration.
> */
> - if (PageHuge(page)) {
> + if (PageTransHuge(page)) {
> struct page *head = compound_head(page);
> unsigned int skip_pages;
>
> - if (!hugepage_migration_supported(page_hstate(head)))
> + if (PageHuge(page) &&
> + !hugepage_migration_supported(page_hstate(head)))
> return page;
>
> skip_pages = compound_nr(head) - (page - head);
> --
> 2.24.1
Everything else looks good to me.
Reviewed-by: Zi Yan <ziy@nvidia.com>
--
Best Regards,
Yan Zi
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next prev parent reply other threads:[~2020-02-21 22:31 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-21 21:53 [PATCH 0/2] fix THP migration for CMA allocations Rik van Riel
2020-02-21 21:53 ` [PATCH 1/2] mm,compaction,cma: add alloc_contig flag to compact_control Rik van Riel
2020-02-24 15:04 ` Vlastimil Babka
2020-02-21 21:53 ` [PATCH 2/2] mm,thp,compaction,cma: allow THP migration for CMA allocations Rik van Riel
2020-02-21 22:31 ` Zi Yan [this message]
2020-02-21 22:35 ` Rik van Riel
2020-02-24 15:29 ` Vlastimil Babka
2020-02-25 18:44 ` Rik van Riel
2020-02-26 9:48 ` Vlastimil Babka
2020-02-26 17:53 ` Rik van Riel
2020-02-28 15:17 ` Vlastimil Babka
2020-03-01 2:24 ` Rik van Riel
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