The patch titled Subject: mm/page_alloc: always attempt to allocate at least one page during bulk allocation has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-page_alloc-always-attempt-to-allocate-at-least-one-page-during-bulk-allocation.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Mel Gorman mgorman@techsingularity.net Subject: mm/page_alloc: always attempt to allocate at least one page during bulk allocation Date: Thu, 26 May 2022 10:12:10 +0100
Peter Pavlisko reported the following problem on kernel bugzilla 216007.
When I try to extract an uncompressed tar archive (2.6 milion files, 760.3 GiB in size) on newly created (empty) XFS file system, after first low tens of gigabytes extracted the process hangs in iowait indefinitely. One CPU core is 100% occupied with iowait, the other CPU core is idle (on 2-core Intel Celeron G1610T).
It was bisected to c9fa563072e1 ("xfs: use alloc_pages_bulk_array() for buffers") but XFS is only the messenger. The problem is that nothing is waking kswapd to reclaim some pages at a time the PCP lists cannot be refilled until some reclaim happens. The bulk allocator checks that there are some pages in the array and the original intent was that a bulk allocator did not necessarily need all the requested pages and it was best to return as quickly as possible.
This was fine for the first user of the API but both NFS and XFS require the requested number of pages be available before making progress. Both could be adjusted to call the page allocator directly if a bulk allocation fails but it puts a burden on users of the API. Adjust the semantics to attempt at least one allocation via __alloc_pages() before returning so kswapd is woken if necessary.
It was reported via bugzilla that the patch addressed the problem and that the tar extraction completed successfully. This may also address bug 215975 but has yet to be confirmed.
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=216007 BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=215975 Link: https://lkml.kernel.org/r/20220526091210.GC3441@techsingularity.net Fixes: 387ba26fb1cb ("mm/page_alloc: add a bulk page allocator") Signed-off-by: Mel Gorman mgorman@techsingularity.net Cc: "Darrick J. Wong" djwong@kernel.org Cc: Dave Chinner dchinner@redhat.com Cc: Jan Kara jack@suse.cz Cc: Vlastimil Babka vbabka@suse.cz Cc: Jesper Dangaard Brouer brouer@redhat.com Cc: Chuck Lever chuck.lever@oracle.com Cc: stable@vger.kernel.org # v5.13+ Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/page_alloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-always-attempt-to-allocate-at-least-one-page-during-bulk-allocation +++ a/mm/page_alloc.c @@ -5324,8 +5324,8 @@ unsigned long __alloc_pages_bulk(gfp_t g page = __rmqueue_pcplist(zone, 0, ac.migratetype, alloc_flags, pcp, pcp_list); if (unlikely(!page)) { - /* Try and get at least one page */ - if (!nr_populated) + /* Try and allocate at least one page */ + if (!nr_account) goto failed_irq; break; } _
Patches currently in -mm which might be from mgorman@techsingularity.net are
mm-page_alloc-always-attempt-to-allocate-at-least-one-page-during-bulk-allocation.patch mm-page_alloc-add-page-buddy_list-and-page-pcp_list.patch mm-page_alloc-use-only-one-pcp-list-for-thp-sized-allocations.patch mm-page_alloc-split-out-buddy-removal-code-from-rmqueue-into-separate-helper.patch mm-page_alloc-protect-pcp-lists-with-a-spinlock.patch