From: Vlastimil Babka <vbabka@suse.cz>
To: Rik van Riel <riel@surriel.com>,
linux-kernel@vger.kernel.org, riel@fb.com
Cc: kernel-team@fb.com, akpm@linux-foundation.org,
linux-mm@kvack.org, mhocko@kernel.org,
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: Mon, 24 Feb 2020 16:29:09 +0100 [thread overview]
Message-ID: <05027092-a43e-756f-4fee-78f29a048ca1@suse.cz> (raw)
In-Reply-To: <3289dc5e6c4c3174999598d8293adf8ed3e93b57.1582321645.git.riel@surriel.com>
On 2/21/20 10:53 PM, Rik van Riel wrote:
> @@ -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));
This continues by:
inc_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
I think it now needs to use mod_node_page_state() with
hpage_nr_pages(page) otherwise the counter will underflow after the
migration?
> 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)) {
Hmm, PageTransHuge() has VM_BUG_ON() for tail pages, while this code is
written so that it can encounter a tail page and skip the rest of the
compound page properly. So I would be worried about this.
Also PageTransHuge() is basically just a PageHead() so for each
non-hugetlbfs compound page this will assume it's a THP, while correctly
it should reach the __PageMovable() || PageLRU(page) tests below.
So probably this should do something like.
if (PageHuge(page) || PageTransCompound(page)) {
...
if (PageHuge(page) && !hpage_migration_supported)) return page.
if (!PageLRU(head) && !__PageMovable(head)) return 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);
>
next prev parent reply other threads:[~2020-02-24 15:29 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
2020-02-21 22:35 ` Rik van Riel
2020-02-24 15:29 ` Vlastimil Babka [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=05027092-a43e-756f-4fee-78f29a048ca1@suse.cz \
--to=vbabka@suse.cz \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=mhocko@kernel.org \
--cc=riel@fb.com \
--cc=riel@surriel.com \
--cc=rientjes@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).