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Wed, 19 Apr 2023 10:36:41 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id KWOUKDnEP2SlMgAAMHmgww (envelope-from ); Wed, 19 Apr 2023 10:36:41 +0000 Message-ID: <804dd674-6078-7455-8dda-1bd921bed828@suse.cz> Date: Wed, 19 Apr 2023 12:36:41 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [RFC PATCH 03/26] mm: make pageblock_order 2M per default Content-Language: en-US To: Johannes Weiner , linux-mm@kvack.org Cc: Kaiyang Zhao , Mel Gorman , David Rientjes , linux-kernel@vger.kernel.org, kernel-team@fb.com, "Kirill A. Shutemov" References: <20230418191313.268131-1-hannes@cmpxchg.org> <20230418191313.268131-4-hannes@cmpxchg.org> From: Vlastimil Babka In-Reply-To: <20230418191313.268131-4-hannes@cmpxchg.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 4EAB81A0006 X-Stat-Signature: wqikxw31yqsd7px4s4bhridcg7sd6cdh X-Rspam-User: X-HE-Tag: 1681900603-33216 X-HE-Meta: U2FsdGVkX1+VAmexPsDiAKlk+uwd+wgT+I92189tvrKjPoAAcftHzxKr4Wda68mpibQDh4YYMcTkjHK2+bIOtnm0sqTvGG9c12ZekWQzPa+Aa77kn+exSPR3bk/3OAE+Ib0wqat6Ub87Fq7fbe4GC9OFcWFu/8R2a9uO+ro9NKXX0K3xtHCPGvGhZGTRR7FPGPD1TldMuzkA3JIpiVbf5WkCJUHmADnYu/RmrOD9RWThDDslfrTKjpZ7ESkA22wew1kagBs0YnGeTFtjFIEyZlATU4MgfxIpGYoIe+XKKy8x4aPJC0LYYxptp9dskaFSesevKjdPsmGfGvWGGPUAQSVEKav4bgTRLEbUAXAEYuIoUJoOq0cSFNiloi0gIdekNSDJv5Ipwn/SwUw0lOJ5jaHYa8lyVBYF6CgD8Qp0FR5bvyAQYSbA/+KyspRhuIQifrtLKIl4VEBTQvV0VwUy0lAkVTU/KyyxCPoYJ5njITNn56H4t3OmLfT5k1FFJrOEluUwEhwyfYytmCW4voR838rgOBNj0C3JFHiJjrE/+tIY0Oyiw3I9jK1XpAOFuZ2trw6ZOrDjgeYZ2rgxd4t4mzU3tzcaZPMzKwnqY3dUZgbTcc52NxczuNuDJlru53gOAc7yd1lU9dUNIuDUKh9Cy5p6MVHpqPNQ+BqnEHdxzbq9+TD3qvK24FRNTPVoqTHEX5ON4eQ77RmDHFGKs4g3NYW19TVmne261/ywk8F8Qy/qZwgj2ImqtIud0gEyqWp8Uj/UZdCGXpxZJJVjZH07lQ9pTLYUT+Ckl0qlaro2R9ac4xVB36FzbmuFuzhGZCVfgeZupFIr2kO8k9Ux/kcmxT67yBorWWqY6OazTUtk5Abvy1XajVbE4z3Oad/tJlfPHzrLyWW09TPQP2NKqfpA2UNeR8xpi6Xkgw7BXKqMp2n9k0BaL+SnuOj3qqZS3ulmIqMPkl5p9xpDjt8nZzA Ez2CMNgC 6Vsgx4X8bWeG/gFWY/OQBSoU94xpoVLJVNmM0Hxv+Fxp+XtnvqdIE4gBOkw12xIgkvZsaMYZN16y6F44+Kn2O/Nf0Ae6XrEGp0LAie/0NydGNkj9Dc3wu6JydApo6m/5XZeqNwh6YDUue9hdS5HIHKOCjq4w5fzqqev0YpTHVCWD4U2tRIqUXUouP7UtdplOIVyJaD3sn9khXQs07eTBsgkk/5QI/cTYOWynd/P6xF3wqp/fMhM7o/gm4Zq1X7ixbtG0deHYmceQ3fiIAPCpQ3l1J6RK8+e/uPycfVydERs38KkBjIjZZJ7ZyFB19z0iqhVBH 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: On 4/18/23 21:12, Johannes Weiner wrote: > pageblock_order can be of various sizes, depending on configuration, > but the default is MAX_ORDER-1. Given 4k pages, that comes out to > 4M. This is a large chunk for the allocator/reclaim/compaction to try > to keep grouped per migratetype. It's also unnecessary as the majority > of higher order allocations - THP and slab - are smaller than that. Well in my experience the kernel usually has hugetlbfs config-enabled so it uses 2MB pageblocks (on x86) even if hugetlbfs is unused at runtime and THP is used instead. But sure, we can set a better default that's not tied to hugetlbfs. > Before subsequent patches increase the effort that goes into > maintaining migratetype isolation, it's important to first set the > defrag block size to what's likely to have common consumers. > > Signed-off-by: Johannes Weiner > --- > include/linux/pageblock-flags.h | 4 ++-- > mm/page_alloc.c | 2 +- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h > index 5f1ae07d724b..05b6811f8cee 100644 > --- a/include/linux/pageblock-flags.h > +++ b/include/linux/pageblock-flags.h > @@ -47,8 +47,8 @@ extern unsigned int pageblock_order; > > #else /* CONFIG_HUGETLB_PAGE */ > > -/* If huge pages are not used, group by MAX_ORDER_NR_PAGES */ > -#define pageblock_order (MAX_ORDER-1) > +/* Manage fragmentation at the 2M level */ > +#define pageblock_order ilog2(2U << (20 - PAGE_SHIFT)) > > #endif /* CONFIG_HUGETLB_PAGE */ > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ac03571e0532..5e04a69f6a26 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7634,7 +7634,7 @@ static inline void setup_usemap(struct zone *zone) {} > /* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */ > void __init set_pageblock_order(void) > { > - unsigned int order = MAX_ORDER - 1; > + unsigned int order = ilog2(2U << (20 - PAGE_SHIFT)); > > /* Check that pageblock_nr_pages has not already been setup */ > if (pageblock_order)