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Fri, 19 Sep 2025 10:03:22 +0800 Message-ID: <229e5cd0-ed50-488c-88d1-c064b83de5a7@huawei.com> Date: Fri, 19 Sep 2025 10:03:21 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/8] mm: page_alloc: optimize pfn_range_valid_contig() To: Zi Yan CC: Andrew Morton , David Hildenbrand , Oscar Salvador , Muchun Song , Matthew Wilcox , , , Vlastimil Babka , Brendan Jackman , Johannes Weiner , References: <20250918132000.1951232-1-wangkefeng.wang@huawei.com> <20250918132000.1951232-2-wangkefeng.wang@huawei.com> Content-Language: en-US From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: kwepems200002.china.huawei.com (7.221.188.68) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 143941A0005 X-Stat-Signature: hksx9r8maorkpowddfm7u71m9xakrnst X-Rspam-User: X-HE-Tag: 1758247407-30800 X-HE-Meta: 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 dHS5JKKR 9r53JuJmP7KMY+EMiPHknRkbRMqxo565B4uc7o8hcCYKQkxvkRYU0cp1zGOkKvl2z4RIkXgiDKjkDVbLcTrN0PltBGLTY+OXt7nVfHpjoSfz6iCS64y/ue8Megcf760LG+2gz4CVh1KlQbxrBR8M3ZBPetmJSTwQcPRfuPlJykdajhpjwbdAEoFCNpo3IyEKAuSzo4qs33uudqN40u4MpmZClU41By0iwmK46tARVZK1BfZC+Cs+gb3PEJ3j4O10FwrY+eMN/fs9gXzs0PAFx+DwEADJChK4EhpUYYe35yu1V670AVRiEUg9elGDjTg361GbtWT7C5sJu6cc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2025/9/18 23:49, Zi Yan wrote: > On 18 Sep 2025, at 9:19, Kefeng Wang wrote: > >> The alloc_contig_pages() spends a lot of time in pfn_range_valid_contig(), >> we could check whether the page in this pfn range could be allocated >> before alloc_contig_range(), if the page can't be migrated, no further >> action is required, and also skip some unnecessary iterations for >> compound pages such as THP and non-compound high order buddy, which >> save times a lot too. The check is racy, but the only danger is skipping >> too much. >> >> A simple test on machine with 116G free memory, allocate 120 * 1G >> HugeTLB folios(107 successfully returned), >> >> time echo 120 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages >> >> Before: 0m2.124s >> After: 0m0.602s >> >> Signed-off-by: Kefeng Wang >> --- >> mm/page_alloc.c | 20 ++++++++++++++++++-- >> 1 file changed, 18 insertions(+), 2 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 478beaf95f84..5b7d705e9710 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -7012,6 +7012,7 @@ static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn, >> { >> unsigned long i, end_pfn = start_pfn + nr_pages; >> struct page *page; >> + struct folio *folio; >> >> for (i = start_pfn; i < end_pfn; i++) { >> page = pfn_to_online_page(i); >> @@ -7021,11 +7022,26 @@ static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn, >> if (page_zone(page) != z) >> return false; >> >> - if (PageReserved(page)) >> + folio = page_folio(page); >> + if (folio_test_reserved(folio)) >> return false; >> >> - if (PageHuge(page)) >> + if (folio_test_hugetlb(folio)) >> return false; >> + >> + /* The following type of folios aren't migrated */ > > s/aren’t/cannot be/ ACK. > >> + if (folio_test_pgtable(folio) | folio_test_stack(folio)) >> + return false; should be "||", will fix. > > Maybe worth explicitly stating these two types of pages in the commit log. > OK, will update. >> + >> + /* >> + * For compound pages such as THP and non-compound high >> + * order buddy pages, save potentially a lot of iterations >> + * if we can skip them at once. >> + */ >> + if (PageCompound(page)) >> + i += (1UL << compound_order(page)) - 1; > > Just a note here, if page is tail, this just move i to the next page > instead of next folio. As no reference held，it is not too precise but we optimize for most scenarios. > >> + else if (PageBuddy(page)) >> + i += (1UL << buddy_order(page)) - 1; >> } >> return true; >> } >> -- >> 2.27.0 > > Otherwise, LGTM. Reviewed-by: Zi Yan > > Thanks. > Best Regards, > Yan, Zi >