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Fri, 27 Oct 2023 07:56:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id mBWHAT5tO2VVJAAAMHmgww (envelope-from ); Fri, 27 Oct 2023 07:56:46 +0000 Message-ID: <6e6435e3-37a5-f613-4333-18df30500847@suse.cz> Date: Fri, 27 Oct 2023 09:56:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [linux-next:master] [mm/slub] 5886fc82b6: will-it-scale.per_process_ops -3.7% regression To: Feng Tang , "Sang, Oliver" Cc: "oe-lkp@lists.linux.dev" , lkp , Linux Memory Management List , Jay Patel , "Huang, Ying" , "Yin, Fengwei" References: <202310202221.fdbcbe56-oliver.sang@intel.com> Content-Language: en-US From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 3B50D2000C X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: muirbz4qgjtjtambfqmkre4jqgwyay4g X-HE-Tag: 1698393407-856525 X-HE-Meta: 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 8SpYcIO/ E+bEK0uYZ/vScvEBlrMr4vBTo3SvwaiWyxKUPC6CwjmcMfJGX+OW8pFKx+fEkk1Ul8VKz41s6O5wXgZ70uUvyQzOEtY3IdWYzschSNwrI2C9s325gmtG5IXXNqhJvYWZqOW045bz3+Fim5YDxf+tKIUrevxVxIk4EcgcBvMokLis2uyGFMPN9wmrIKTvxN14vLMcAaPW6LiOk+0OS+H6RXCBUgOywIHZXDEa2ffDpH6eyXI5HJiwciXjc4/uVRqHW/S5Ov2aPBRwqWQVr2vY2xb03l2LV+WKiHT0BL9qNVrnJzN0tKstkf118LbDi/LQWkCeDbG/SzrYnoa5AN8Nuh7Py4r7mq8Ipao8aZ9wef4LyBAE= 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 10/27/23 09:40, Feng Tang wrote: > On Fri, Oct 20, 2023 at 10:21:28PM +0800, Sang, Oliver wrote: >> >> >> Hello, >> >> kernel test robot noticed a -3.7% regression of will-it-scale.per_process_ops on: > > I was surprised to see this initially, as I know this patch which > only affects the order of a few slabs in a certain size range, and > 0Day has enabled the 64 bytes alignment for function address. > > One only big difference of perf hot spot is > >> 19.62 +1.9 21.54 perf-profile.self.cycles-pp.__fget_light > > but its code flow and data doesn't have much to do with the commit. > > I manually run the test case, and didn't see the affected slabs > actively used by checking 'slabtop' > > Then I hacked to move slub.c to a very late position when linking > kernel image, so that very few other kernel modules' alignment will > be affected, and the regression is gone. > > So this seems to be another strange perf change caused by text code > alignment changes. similar to another recent case of MCE patch > https://lore.kernel.org/lkml/202310111637.dee70328-oliver.sang@intel.com/ I suspected it would be something like this, thanks for confirming!