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b=pdaA2Lg8+hnR4r/HJkpqMkOJmX2luIHLB6VEzjqCo2bMtFP3A4SkvhwObmMiYZKrKhBzVhApus5zruhtjAdiFHXpnEStHAXqI+iHu8vt10kIeKY44IPpDKKOdGd9NZ0uaINO/NYICfGoN6ySZ+nmE9HZYbRWjpA/7zZs3bfhzRg= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046056;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0W3uSCUF_1712233169; Received: from 30.120.150.29(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0W3uSCUF_1712233169) by smtp.aliyun-inc.com; Thu, 04 Apr 2024 20:19:30 +0800 Message-ID: <30bef3d6-3381-491e-a00a-bd1fb7e8d8f8@linux.alibaba.com> Date: Thu, 4 Apr 2024 20:19:29 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: page_alloc: use the correct THP order for THP PCP To: Vlastimil Babka , akpm@linux-foundation.org Cc: mgorman@techsingularity.net, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <76457ec5-d789-449b-b8ca-dcb6ceb12445@suse.cz> From: Baolin Wang In-Reply-To: <76457ec5-d789-449b-b8ca-dcb6ceb12445@suse.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 4CDE51C0021 X-Stat-Signature: bzdz5gogeq54ihut99hbmoyytmsu7jtq X-HE-Tag: 1712233173-226933 X-HE-Meta: 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 uJTjmCZI w3Bd0lNBDWjIJce6wlv5fyPfvm25ZR68e831gLhPYjcts+i3PsBq+RYHjE2oJVxc6fRwa3wx2yFP5t8fULBwZWgdww6MDfqCaD71C8YGK406LRobbKABoCnV+eAMPDVH97AeT/vRrRVceOjRQ1TeDeYI56PVuQdZ3XxbRqujdnEOpNam3m7qL0Fh8FrsqfnvnRpde8qCNPaIfg6+nY6UK3X2eAkD74F0PRjs06pvDtndyW0xrwtxZfpRrzeVoriCD2+VEFzr8CZXbXTsu6N1L3tlXxg== 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 2024/4/4 18:03, Vlastimil Babka wrote: > On 4/3/24 3:47 PM, Baolin Wang wrote: >> Commit 44042b449872 ("mm/page_alloc: allow high-order pages to be stored >> on the per-cpu lists") extends the PCP allocator to store THP pages, and >> it determines whether to cache THP pags in PCP by comparing with pageblock_order. >> But the pageblock_order is not always equal to THP order, it might also >> be MAX_PAGE_ORDER, which could prevent PCP from caching THP pages. >> >> Therefore, using HPAGE_PMD_ORDER instead to determine the need for caching >> THP for PCP can fix this issue >> >> Fixes: 44042b449872 ("mm/page_alloc: allow high-order pages to be stored on the per-cpu lists") >> Signed-off-by: Baolin Wang > > IIUC this happens with CONFIG_HUGETLB_PAGE disabled because HUGETLBFS is > disabled? But THPs are still enabled? I think there might be more of THP Right, and seems the Powerpc arch will set pageblock_order via set_pageblock_order() when the huge page sizes are variable (not sure if this is always equal to THP order). Moreover, it still does not make sense to use pageblock_order to indicate a THP page, especially when we already have HPAGE_PMD_ORDER to represent THP. > working suboptimally in that case with pageblock_order being larger > (MAX_PAGE_ORDER). > > In other words, should be rather make pageblock_order itself defined as > > min_t(unsigned int, HPAGE_PMD_ORDER, MAX_PAGE_ORDER) > > in case with !CONFIG_HUGETLB_PAGE but THP enabled. Yes, this makes sense to me (I wonder why this wasn't done before?). I can create a seperate patch to do this, what do you think? Thanks.