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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v8 1/4] kselftest: mm: prevent random failure of huge page split for khugepaged Message-ID: References: <20260924-fix_split-v8-0-cba7359d882a@arm.com> <20260924-fix_split-v8-1-cba7359d882a@arm.com> <07f94688-55ed-407a-a11a-78a4feedf5e2@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <07f94688-55ed-407a-a11a-78a4feedf5e2@arm.com> X-Stat-Signature: 1kyqgxygugxdsrydyjy9h5bfagrxxw71 X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 62F1C20002 X-HE-Tag: 1790346325-411288 X-HE-Meta: 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 beQPdtrx flLfaF7iO32/uxnZ0eD9IJzGKep6EtHfzf1HLXsL7PWG6m1t6KL9s5j3yKmtCZ4QxDcxLHe2rQ2qGiF0cNc2Pmwdodc9s3vF4g0aDvIElYlk4Vm/IIBy5io9ELKxEEdGIjfbnikklVTAYQhEGHG0NBQnIGwGtcxSONZWcqzRHkcLAi8d7FIArXJzImy284gWa+AFy3NBbcq5bFf/2Jqy2xb8eWkOponn1huscLds1w+iMNCAwK0G3p4WVJvFevtSQ7qy7tf9UGcQG6uV3e6cUAxkg2YV/fdlcIitKiU3Pw9+A9SzchhhMd88Bt3tSSOFL5E4VxVCZWGmB8i61NSFDpm3XDQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > > On 9/25/26 12:41 AM, Yeoreum Yun wrote: > > There're some random failure for split_huge_page_test when khugepaged > > collapses pages into pmd again which had split by the test. > > > > Prevent the khugepaged's collapses for split page by setting the > > mapped pmd-huge-page with MADV_NOHUGEPAGE before split. > > > > Suggested-by: Kevin Brodsky > > Suggested-by: Lorenzo Stoakes (ARM) > > Reviewed-by: Lorenzo Stoakes (ARM) > > Reviewed-by: Zi Yan > > Acked-by: David Hildenbrand (Arm) > > Signed-off-by: Yeoreum Yun > > --- > > tools/testing/selftests/mm/split_huge_page_test.c | 19 +++++++++++++++++++ > > 1 file changed, 19 insertions(+) > > > > diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c > > index c5d96a4b1db3..ef4058662b91 100644 > > --- a/tools/testing/selftests/mm/split_huge_page_test.c > > +++ b/tools/testing/selftests/mm/split_huge_page_test.c > > @@ -108,6 +108,18 @@ static char *allocate_zero_filled_hugepage(size_t len) > > return result; > > } > > > > +static void disable_khugepaged(void *addr, size_t len) > > +{ > > + /* > > + * Disables khugepaged from collapsing THPs in range, existing THP > > Should it be "collapsing pages in range into THPs" instead? That would be clear. I'll change with it. > > > + * pages remain. > > + */ > > + if (!madvise(addr, len, MADV_NOHUGEPAGE)) > > + return; > > + > > + ksft_exit_fail_msg("MADV_NOHUGEPAGE failed, err=%d\n", errno); > > I feel a ksft_exit_fail_perror() would be better here, since it will > automatically print strerror(errno) as well. Still, it is not something > that should require a respin of its own, so if you plan to respin for > some other changes, you might fold these changes in as well. Yeap. I'll change it with _perror. > > Rest looks good, so: > > Reviewed-by: Sarthak Sharma > > > +} > > + > > static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hpages, size_t len) > > { > > unsigned long rss_anon_before, rss_anon_after; > > @@ -120,6 +132,8 @@ static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hp > > if (!rss_anon_before) > > ksft_exit_fail_msg("No RssAnon is allocated before split\n"); > > > > + disable_khugepaged(one_page, len); > > + > > /* split all THPs */ > > write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, > > (uint64_t)one_page + len, 0); > > @@ -167,6 +181,8 @@ static void split_pmd_thp_to_order(int order) > > if (!check_huge_anon(one_page, 4 * pmd_pagesize, 4, pmd_pagesize)) > > ksft_exit_fail_msg("No THP is allocated\n"); > > > > + disable_khugepaged(one_page, len); > > + > > /* split all THPs */ > > write_debugfs(PID_FMT, getpid(), (uint64_t)one_page, > > (uint64_t)one_page + len, order); > > @@ -215,6 +231,8 @@ static void split_pte_mapped_thp(void) > > goto out; > > } > > > > + disable_khugepaged(thp_area, thp_area_size); > > + > > /* > > * To challenge spitting code, we will mremap a single page of each > > * THP (page[i] of thp[i]) in the thp_area into page_area. This will > > @@ -482,6 +500,7 @@ static int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, > > ksft_test_result_skip("Pagecache folio split skipped\n"); > > return -2; > > } > > + disable_khugepaged(*addr, fd_size); > > return 0; > > err_out_close: > > close(*fd); > > > -- Sincerely, Yeoreum Yun