Re: [PATCH v5 8/8] mm: huge_memory: enable debugfs to split huge pages to any order.

From: Aishwarya TCV <aishwarya.tcv@arm.com>
To: Zi Yan <ziy@nvidia.com>,
	"Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>,
	linux-mm@kvack.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	"David Hildenbrand" <david@redhat.com>,
	"Yang Shi" <shy828301@gmail.com>, "Yu Zhao" <yuzhao@google.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	"Ryan Roberts" <ryan.roberts@arm.com>,
	"Michal Koutný" <mkoutny@suse.com>,
	"Roman Gushchin" <roman.gushchin@linux.dev>,
	"Zach O'Keefe" <zokeefe@google.com>,
	"Hugh Dickins" <hughd@google.com>,
	"Luis Chamberlain" <mcgrof@kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	"Mark Brown" <broonie@kernel.org>
Subject: Re: [PATCH v5 8/8] mm: huge_memory: enable debugfs to split huge pages to any order.
Date: Fri, 1 Mar 2024 09:51:19 +0000	[thread overview]
Message-ID: <082e48c8-71b7-4937-a5da-7a37b4be16ba@arm.com> (raw)
In-Reply-To: <20240226205534.1603748-9-zi.yan@sent.com>

On 26/02/2024 20:55, Zi Yan wrote:
> From: Zi Yan <ziy@nvidia.com>
> 
> It is used to test split_huge_page_to_list_to_order for pagecache THPs.
> Also add test cases for split_huge_page_to_list_to_order via both
> debugfs.
> 
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>  mm/huge_memory.c                              |  34 ++++--
>  .../selftests/mm/split_huge_page_test.c       | 115 +++++++++++++++++-
>  2 files changed, 131 insertions(+), 18 deletions(-)
> 

Hi Zi,

When booting the kernel against next-master(20240228)with Arm64 on
Marvell Thunder X2 (TX2), the kselftest-mm test 'split_huge_page_test'
is failing in our CI (with rootfs over NFS). I can send the full logs if
required.

A bisect (full log below) identified this patch as introducing the
failure. Bisected it on the tag "next-20240228" at repo
"https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git".

This works fine on  Linux version 6.8.0-rc6

Sample log from failure against run on TX2:
------
07:17:34.056125  # # ------------------------------
07:17:34.056543  # # running ./split_huge_page_test
07:17:34.056839  # # ------------------------------
07:17:34.057114  # # TAP version 13
07:17:34.058564  # # 1..12
07:17:34.156822  # # ok 1 Split huge pages successful
07:17:34.214074  # # ok 2 Split PTE-mapped huge pages successful
07:17:34.215630  # # # Please enable pr_debug in
split_huge_pages_in_file() for more info.
07:17:34.225503  # # # Please check dmesg for more information
07:17:34.225862  # # ok 3 File-backed THP split test done
07:17:34.236944  # # Bail out! Failed to create a file at /mnt/thp_fs#
Planned tests != run tests (12 != 3)
07:17:34.237307  # # # Totals: pass:3 fail:0 xfail:0 xpass:0 skip:0 error:0
07:17:34.237620  # # [FAIL]
07:17:34.246430  # not ok 51 split_huge_page_test # exit=1

Bisect log:
------
git bisect start
# good: [d206a76d7d2726f3b096037f2079ce0bd3ba329b] Linux 6.8-rc6
git bisect good d206a76d7d2726f3b096037f2079ce0bd3ba329b
# bad: [20af1ca418d2c0b11bc2a1fe8c0c88f67bcc2a7e] Add linux-next
specific files for 20240228
git bisect bad 20af1ca418d2c0b11bc2a1fe8c0c88f67bcc2a7e
# bad: [1322f1801e59dddce10591d602d246c1bf49990c] Merge branch 'main' of
git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
git bisect bad 1322f1801e59dddce10591d602d246c1bf49990c
# bad: [a82f70041487790b7b09fe4bb45436e1b57021d3] Merge branch 'dev' of
git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git
git bisect bad a82f70041487790b7b09fe4bb45436e1b57021d3
# bad: [ce90480b9352ba2bebe8946dad9223e3f24c6e9a] Merge branch
'for-next' of
git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap.git
git bisect bad ce90480b9352ba2bebe8946dad9223e3f24c6e9a
# bad: [5daac92ed3881fd0c656478a301a4e1d124100ee] Merge branch
'mm-everything' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
git bisect bad 5daac92ed3881fd0c656478a301a4e1d124100ee
# good: [acc2643d9e988c63dd4629a9af380ad9ac69c54a] Merge branch
'mm-stable' into mm-unstable
git bisect good acc2643d9e988c63dd4629a9af380ad9ac69c54a
# good: [0294de8fe7d7c1a7eddc979cbf4c1886406e36b7] Merge branch 'fixes'
of git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-power-supply.git
git bisect good 0294de8fe7d7c1a7eddc979cbf4c1886406e36b7
# good: [83e0c8f0e777a1ef0977b2f8189101765703b32d] Merge branch
'mm-nonmm-stable' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
git bisect good 83e0c8f0e777a1ef0977b2f8189101765703b32d
# good: [a739cbe236e0dd3b6ff26a01fa1d31c73d4fac93] mm: memcg: make memcg
huge page split support any order split
git bisect good a739cbe236e0dd3b6ff26a01fa1d31c73d4fac93
# bad: [efb520aa333b2f11daaaaa13f4a598b5ae4ae823] mm: allow non-hugetlb
large folios to be batch processed
git bisect bad efb520aa333b2f11daaaaa13f4a598b5ae4ae823
# bad: [2258bdebb55e3ad3d30fd3849ddb955ff36825de] mm/zsmalloc: don't
hold locks of all pages when free_zspage()
git bisect bad 2258bdebb55e3ad3d30fd3849ddb955ff36825de
# bad: [7fc0be45acf2878cbacc4dba56923c34c3fd8b1e] mm: remove
total_mapcount()
git bisect bad 7fc0be45acf2878cbacc4dba56923c34c3fd8b1e
# good: [d55fac55da2f87ad5a99178e107df09770bbc411] mm: thp: split huge
page to any lower order pages
git bisect good d55fac55da2f87ad5a99178e107df09770bbc411
# bad: [4050d591c1aaf9336c08511fa5984827186e9ad1] mm/memfd: refactor
memfd_tag_pins() and memfd_wait_for_pins()
git bisect bad 4050d591c1aaf9336c08511fa5984827186e9ad1
# bad: [c0ba89c29ef559c95273feb481b049f622c43c17] mm: huge_memory:
enable debugfs to split huge pages to any order
git bisect bad c0ba89c29ef559c95273feb481b049f622c43c17
# first bad commit: [c0ba89c29ef559c95273feb481b049f622c43c17] mm:
huge_memory: enable debugfs to split huge pages to any order

Thanks,
Aishwarya