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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 14B424000A X-Stat-Signature: 31dfn3ro8htr7syrq3n3ryd7xjjbkpjm X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1758771495-894908 X-HE-Meta: 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 5+eA0JI6 69O+19w9obpUXiYlCTMZQehQy6WL/fcHXYJTV8KgztwKwc0B4JYnY1cmlHQ7IsCWsJiSD2hSal0VxcUrrT68CiO47lcSqqIbqIw6voT5a2g/Z7LffLGLqZINLH5dsO4fcl9fhVgL6U5cSF8jHoR7PE3ngNfkZxgkzO3F7BKE2Aq3p0Sx7JgWTef3uC+6N1aq5uXXDGAVUTYBFp7tso/HfBZFBQsML8yeQ20axeiJOBwBU6qdnavHTOEdY/A== 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 25/09/25 7:02 am, Huang, Ying wrote: > Hi, Haoran, > > Zhu Haoran writes: > >> Hi! >> >> I recently noticed the process_huge_page function in memory.c, which was >> intended to keep the cache hotness of target page after processing. I compared >> the vm-scalability anon-cow-seq-hugetlb microbench using the default >> process_huge_page and sequential processing (code posted below). >> >> I ran test on epyc-7T83 with 36vCPUs and 64GB memory. Using default >> process_huge_page, the avg bandwidth is 1148 mb/s. However sequential >> processing yielded a better bandwidth of about 1255 mb/s and only >> one-third cache-miss rate compared with default one. >> >> The same test was run on epyc-9654 with 36vCPU and 64GB mem. The >> bandwidth result was similar but the difference was smaller: 1170mb/s >> for default and 1230 mb/s for sequential. Although we did find the cache >> miss rate here did the reverse, since the sequential processing seen 3 >> times miss more than the default. >> >> These result seem really inconsitent with the what described in your >> patchset [1]. What factors might explain these behaviors? > One possible difference is cache topology. Can you try to bind the test > process to the CPUs in one CCX (that is, share one LLC). This make it > possible to hit the local cache. Hi, I just had a different question, why is the function sprinkled with cond_resched() in each loop, especially the last one in which we are calling it every iteration? I suppose one reason for slowdown may be this too. > >> Thanks for your time. >> >> [1] https://lkml.org/lkml/2018/5/23/1072 >> >> --- >> Sincere, >> Zhu Haoran >> >> --- >> >> static int process_huge_page( >> unsigned long addr_hint, unsigned int nr_pages, >> int (*process_subpage)(unsigned long addr, int idx, void *arg), >> void *arg) >> { >> int i, ret; >> unsigned long addr = addr_hint & >> ~(((unsigned long)nr_pages << PAGE_SHIFT) - 1); >> >> might_sleep(); >> for (i = 0; i < nr_pages; i++) { >> cond_resched(); >> ret = process_subpage(addr + i * PAGE_SIZE, i, arg); >> if (ret) >> return ret; >> } >> >> return 0; >> } > --- > Best Regards, > Huang, Ying >