On Tue, 11 Jul 2023 13:20:20 -0400 Yu Ma <yu.ma@xxxxxxxxx> wrote: > UnixBench/Execl represents a class of workload where bash scripts are > spawned frequently to do some short jobs. When running multiple parallel > tasks, hot osq_lock is observed from do_mmap and exit_mmap. Both of them > come from load_elf_binary through the call chain > "execl->do_execveat_common->bprm_execve->load_elf_binary". In do_mmap,it will > call mmap_region to create vma node, initialize it and insert it to vma > maintain structure in mm_struct and i_mmap tree of the mapping file, then > increase map_count to record the number of vma nodes used. The hot osq_lock > is to protect operations on file’s i_mmap tree. For the mm_struct member > change like vma insertion and map_count update, they do not affect i_mmap > tree. Move those operations out of the lock's critical section, to reduce > hold time on the lock. > > With this change, on Intel Sapphire Rapids 112C/224T platform, based on > v6.0-rc6, the 160 parallel score improves by 12%. The patch has no > obvious performance gain on v6.4-rc4 due to regression of this benchmark > from this commit f1a7941243c102a44e8847e3b94ff4ff3ec56f25 (mm: convert > mm's rss stats into percpu_counter). Related discussion and conclusion > can be referred at the mail thread initiated by 0day as below: > Link: https://lore.kernel.org/linux-mm/a4aa2e13-7187-600b-c628-7e8fb108def0@xxxxxxxxx/ Could you please redo/retest this against a kernel which has 1c7873e3364 ("mm: lock newly mapped VMA with corrected ordering")? mainline, mm-unstable or linux-next. Thanks.
