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Sat, 30 Aug 2025 00:46:28 -0700 (PDT) Date: Sat, 30 Aug 2025 07:46:27 +0000 From: Wei Yang To: Andrew Morton Cc: Wei Yang , david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH] selftests/mm: directly add pagesize instead of increase until page size Message-ID: <20250830074627.pitdp64svss6slyk@master> Reply-To: Wei Yang References: <20250830023102.14981-1-richard.weiyang@gmail.com> <20250829200953.1757e85542b1126c4881d600@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250829200953.1757e85542b1126c4881d600@linux-foundation.org> User-Agent: NeoMutt/20170113 (1.7.2) On Fri, Aug 29, 2025 at 08:09:53PM -0700, Andrew Morton wrote: >On Sat, 30 Aug 2025 02:31:02 +0000 Wei Yang wrote: > >> The check of is_backed_by_folio() is done on each page. >> >> Directly move pointer to next page instead of increase one and check if >> it is page size aligned. > >Why? > >> --- a/tools/testing/selftests/mm/split_huge_page_test.c >> +++ b/tools/testing/selftests/mm/split_huge_page_test.c >> @@ -423,9 +423,8 @@ static void split_pte_mapped_thp(void) >> >> /* smap does not show THPs after mremap, use kpageflags instead */ >> thp_size = 0; >> - for (i = 0; i < pagesize * 4; i++) >> - if (i % pagesize == 0 && >> - is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpageflags_fd)) >> + for (i = 0; i < pagesize * 4; i += pagesize) >> + if (is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpageflags_fd)) >> thp_size++; > >Looks like we're doing more work. Is there something wrong with the >existing code? Excuse me if I misunderstand the code. Originally, i iterate from 0 to pagesize * 4 one by one and call is_backed_by_folio() when i is 0, 4096, 8192, 12288. The change makes i just iterate on 0, 4096, 8192, 12288 and call is_backed_by_folio() respectively. Current code is not wrong, but not necessary to iterate one by one. -- Wei Yang Help you, Help me