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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 v4 1/3] kselftest: mm: prevent random failure of huge page split for khugepaged Message-ID: References: <20260902-fix_split-v4-0-85f03905f7b1@arm.com> <20260902-fix_split-v4-1-85f03905f7b1@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: pkphzwpbn15k4o3m3a8r5ii31trg17g3 X-Rspamd-Queue-Id: 2398040011 X-Rspamd-Server: rspam06 X-HE-Tag: 1788363189-577494 X-HE-Meta: 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 JnAQhFg4 pc+1bsxymZgq6WPnGWr7LPl9+qNrU8q4xyxEwRg/c9RZUvetRFpzeluVUxcoZpMdSKPKB5QNdsSphiGf7F0708In2QmrCJJ6lz95hrs+ssrtD1sUq+hG3niXv+4xuWMyQx1nOSvfxu3vfunfDAxEgDjQ04+DwIzD2C+uonqn1zHVFvdnCAHcaamrFlS2KU4lmzr6fI/XWsSQs2HXr1HRJcRXqumohscYMynasj/ozVK7nnwNU9m666VxGhktEowdMiumwS6p791aUf7X0b5FWIdcj+anJGS8ByEolh5M7qvc63o33pFbZsb0FgCbi350j3SDq Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 02, 2026 at 04:15:17PM +0100, Lorenzo Stoakes (ARM) wrote: > On Wed, Sep 02, 2026 at 01:09:35PM +0100, 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. > > Maybe worth saying that MADV_NOHUGEPAGE doesn't immediately split anything, just > prevents future khugepaged collapses? > > > > > Suggested-by: Kevin Brodsky > > Suggested-by: Lorenzo Stoakes (ARM) > > Signed-off-by: Yeoreum Yun > > LGTM, thanks, with a few nits above/below (sorry! :P) > > Reviewed-by: Lorenzo Stoakes (ARM) > > > --- > > 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 86a603692826..4bbad892bc57 100644 > > --- a/tools/testing/selftests/mm/split_huge_page_test.c > > +++ b/tools/testing/selftests/mm/split_huge_page_test.c > > @@ -168,6 +168,14 @@ static char *allocate_zero_filled_hugepage(size_t len) > > return result; > > } > > > > +static void madv_nohuge(void *addr, size_t len) > > Maybe call it disable_khugepaged() to make it explicit that's what this is doing > rather than eliminating any THP pages in the range? > > > +{ > > Maybe a comment here like: > > /* > * Disables khugepaged from collapsing THPs in range, existing THP > * pages remain. > */ Okay :) I'll modify in the next-round. Thanks! [...] -- Sincerely, Yeoreum Yun