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b=DFpxpa+VDyNxFf3wVwCAF/LrGoNlRgRvjCjGTRjTjKfT4b+1fxGv/ERL6jGnk2PQl yraZ0E7SjbWBuA0PnC1IFVFYoD9mmYEnFP2xz+zsYePqKxveL19B0ISHA0XDziIU1S a6SizlDZ+Vfspvye/2EmHO8a10niwF6mpV9TNCaalVchQZLw+HR5hOwfI4Olrom9N+ a8LX0Q+qYh0As+JMMfExsdyDHC2JsKT56vTLNXMt8egX5RSXG6zrTH022Z1fv/yNO7 4KsDW8Hfjf6KXdmEcOuuqEhUOGlN3W+mLKB1CnAhuwWBY6F4o1J9p16Cij8NTglZ6p lhWMYA4QM9msA== Date: Tue, 18 Aug 2026 11:12:39 +0100 From: "Lorenzo Stoakes (ARM)" To: Kiryl Shutsemau Cc: akpm@linux-foundation.org, david@kernel.org, nico.pache@linux.dev, baolin.wang@linux.alibaba.com, baohua@kernel.org, dev.jain@arm.com, hughd@google.com, lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com, rppt@kernel.org, ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, ziy@nvidia.com, usama.anjum@arm.com, agordeev@linux.ibm.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, kas@kernel.org Subject: Re: [PATCH v4 06/19] selftests/mm: stop khugepaged during the MADV_COLLAPSE cases Message-ID: References: <20260815015901.1236937-1-kirill@shutemov.name> <20260815015901.1236937-7-kirill@shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260815015901.1236937-7-kirill@shutemov.name> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 103BF80004 X-Stat-Signature: e3wi6nytxa8833sxb4qbi1c1pac7b5a5 X-Rspam-User: X-HE-Tag: 1787047981-851337 X-HE-Meta: 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 QqAKR21j 9RSYkCwzeOXWG15yJkkTYfGsBAhJW0dF2PTZ5j8Bm5iixDOamBVaRINREOh91gvdvlkmyMfMjuZDUtTP9OdENhpZT7HnOEF2nn2RaPkk7IXKhZpl1oX0kvHZD+Uspjd/vvvhuvQykgNeDKgbLNOWw9x1DOoM0TniFdwWPsCOOlORkNyjG0E7764Sjms1/14/8MTq9WPwtdLlwIMH0bpfjEUMG+CooJZbUjFmk6RNVy/RvQ/etLet+VYMVU0N8MRlNKRf82Jd2EYraf6Obe3dreHh71CmPmn/ARQCkZX2PRTpICPVClOhovpD3qvkTuXLopEBOAASf15tb7Qo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Aug 15, 2026 at 02:58:48AM +0100, Kiryl Shutsemau wrote: > From: "Kiryl Shutsemau (Meta)" > > __madvise_collapse() turns THP off before each MADV_COLLAPSE, both to keep > khugepaged out of the range and to prove MADV_COLLAPSE ignores the setting. > It clears the global controls only, which is no longer enough. A per-order > control overrides them, and -s leaves the source order at "always", so > khugepaged collapses the very range the case is working on. The case then > fails on a collapse that was interfered with rather than refused. > > Clear the per-order controls too. Set them to "inherit", not "never". > khugepaged honours the global never and stays out. A forced shmem collapse > takes the order it builds from these very controls, and still finds one. > > Fixes: 9f0704eae8a4 ("selftests/mm/khugepaged: enlighten for multi-size THP") > Assisted-by: Claude-Code:claude-opus-5 > Signed-off-by: Kiryl Shutsemau (Meta) > --- > tools/testing/selftests/mm/khugepaged.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c > index 7eb9db0005a0..0008862e7cbc 100644 > --- a/tools/testing/selftests/mm/khugepaged.c > +++ b/tools/testing/selftests/mm/khugepaged.c > @@ -550,8 +550,8 @@ static bool is_anon(struct mem_ops *ops) > static void __madvise_collapse(const char *msg, char *p, int nr_hpages, > struct mem_ops *ops, bool expect) > { > - int ret; > struct thp_settings settings = *thp_current_settings(); > + int ret, i; > > ksft_print_msg("%s...", msg); > > @@ -564,9 +564,20 @@ static void __madvise_collapse(const char *msg, char *p, int nr_hpages, > /* > * Prevent khugepaged interference and tests that MADV_COLLAPSE > * ignores /sys/kernel/mm/transparent_hugepage/enabled > + * > + * The per-order controls have to go too, not just the global one: a > + * source order left at "always" -- which -s does -- lets khugepaged > + * collapse the very range the case is working on. Set them to > + * "inherit", not "never". khugepaged honours the global never and > + * stays out. A forced shmem collapse takes the order it builds from > + * these very controls, and still finds one. Again far too many words, schloppy. Trim it please. This isn't a chat with claude it's a comment. > */ > settings.thp_enabled = THP_NEVER; > settings.shmem_enabled = SHMEM_NEVER; > + for (i = 0; i < NR_ORDERS; i++) { > + settings.hugepages[i].enabled = THP_INHERIT; > + settings.shmem_hugepages[i].enabled = SHMEM_INHERIT; > + } > thp_push_settings(&settings); > > /* Clear VM_NOHUGEPAGE */ > -- > 2.54.0 > -- Cheers, Lorenzo