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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Peter Xu , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , Shuah Khan , Jason Gunthorpe , Leon Romanovsky , Sarthak Sharma Subject: Re: [PATCH v3 3/3] kselftest: mm: introduce size_to_shift() helper Message-ID: References: <20260914-fix_hpage_macro-v3-0-c9a305a01d39@arm.com> <20260914-fix_hpage_macro-v3-3-c9a305a01d39@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 2B38040007 X-Rspam-User: X-Stat-Signature: xhke8ix9cyqte4q1gxf1uuumrhhbfw64 X-HE-Tag: 1789465647-502796 X-HE-Meta: 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 VFMCASX6 Xp5Aybo+sbzsM/YzUQ7v7WlJz6IpNfk3+CzCzld56tBrBPwaydsym0taqlOiTC8rqHlvDUjiGwulVyXKboaM3xcFkx3zonaZpRkRKgVC57CQwcE33E5ZZgJEHrUxuRzHBlXg0JfyFqETawrIRVn1InmGb9uvnKuxTd5Yx7PKXLYwl9GmVA4Qjqozi9ssTZeU0Ophlremyl+X0ZxVB/cXIoQw+lH8jwsmyXE+R6/QQAXq8ipJXhJfPEEs/Ml1fa9NhavXopUkUVptAQ54YSimZnHZMIw2nDkacdCapRJpHNumIZa2/i5ZYE3DIhxffG65uW3hNGYLfnImlheDYZKur+fSCfVNDUzsYBkZ9CzSNXqR78Xg96vBW+JEU9g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Sep 15, 2026 at 10:01:58AM +0100, Lorenzo Stoakes (ARM) wrote: > On Mon, Sep 14, 2026 at 04:08:30PM +0200, David Hildenbrand (Arm) wrote: > > On 9/14/26 16:06, Yeoreum Yun wrote: > > > On Mon, Sep 14, 2026 at 04:01:02PM +0200, David Hildenbrand (Arm) wrote: > > >> On 9/14/26 09:30, Yeoreum Yun wrote: > > >>> Introduce size_to_shift() for future users that need to > > >>> obtain shift of a huge-page which is other than pmd_psize(). > > >>> > > >>> Suggested-by: David Hildenbrand (Arm) > > >>> Signed-off-by: Yeoreum Yun > > >>> --- > > >>> tools/testing/selftests/mm/vm_util.c | 10 +++++++++- > > >>> tools/testing/selftests/mm/vm_util.h | 1 + > > >>> 2 files changed, 10 insertions(+), 1 deletion(-) > > >>> > > >>> diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > > >>> index fd1432dc6152..1fef1266429f 100644 > > >>> --- a/tools/testing/selftests/mm/vm_util.c > > >>> +++ b/tools/testing/selftests/mm/vm_util.c > > >>> @@ -157,6 +157,14 @@ bool check_for_pattern(FILE *fp, const char *pattern, char *buf, size_t len) > > >>> return false; > > >>> } > > >>> > > Probably worth a comment here saying it's only for power-of-two sizes. Okay. > > > >>> +uint64_t size_to_shift(uint64_t size) > > >>> +{ > > >>> + if (__builtin_popcountll(size) != 1) > > I wonder if it wouldn't be better to just do the old trick of: > > if (!size || (size & (size - 1))) > return 0; > > ? > > > >>> + return 0; > > >>> + > > >>> + return ffsl(size) - 1; > > >>> +} > > >> > > >> Could likely just be an inline helper? > > > > > > Okay. If there is no comments on today, I'll post tomorrow with this. > > > > > > > No need to rush, leave some more days for people to catch up. > > Agree with David seems better as an inline thing, the __builtin_xxx() should > be... built-in hopefully :P though I suggest something that wouldn't need that. Whatever is, okay. I'll change with old-classic trick :) > > As long as strings.h is included in the header ofc for ffsl(). > > With the stuff above addressed, seems fine to me so: > > Reviewed-by: Lorenzo Stoakes (ARM) Thanks! > > > > > -- > > Cheers, > > > > David > > -- > Cheers, Lorenzo -- Sincerely, Yeoreum Yun