---- 在 星期五, 2020-10-30 23:46:00 Miklos Szeredi <miklos@xxxxxxxxxx> 撰写 ---- > On Sun, Oct 25, 2020 at 4:42 AM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote: > > > > Current syncfs(2) syscall on overlayfs just calls sync_filesystem() > > on upper_sb to synchronize whole dirty inodes in upper filesystem > > regardless of the overlay ownership of the inode. In the use case of > > container, when multiple containers using the same underlying upper > > filesystem, it has some shortcomings as below. > > > > (1) Performance > > Synchronization is probably heavy because it actually syncs unnecessary > > inodes for target overlayfs. > > > > (2) Interference > > Unplanned synchronization will probably impact IO performance of > > unrelated container processes on the other overlayfs. > > > > This series try to implement containerized syncfs for overlayfs so that > > only sync target dirty upper inodes which are belong to specific overlayfs > > instance. By doing this, it is able to reduce cost of synchronization and > > will not seriously impact IO performance of unrelated processes. > > Series looks good at first glance. Still need to do an in-depth review. > > In the meantime can you post some numbers showing the performance improvements? > Actually, the performance improvement depends on workload and the number of overlay instances. I did a very simple test on my dev box (intel NUC ) and the result seems quite obvious. I made two overlay instances and untar a kernel source to an overlay then compare umount time(sys part) of two instances. ------------------------------------------ test env: Intel(R) Core(TM) i7-8809G CPU @ 3.10GHz 8core 32GB memory Samsung NVMe SSD 970 pro test script: [root@localhost ovl]# cat do.sh #!/bin/sh rm -rf upper/* &> /dev/null echo 3 > /proc/sys/vm/drop_caches mount -t overlay overlay -o lowerdir=lower,workdir=work,upperdir=upper merged mount -t overlay overlay -o lowerdir=lower2,workdir=work2,upperdir=upper2 merged2 tar Jxvf linux-5.9.tar.xz -C merged &> /dev/null time umount merged2 time umount merged --------------------------------- test result: [root@localhost ovl]# seq 3 | while read line ; do sh -x do.sh ; done + rm -rf upper/linux-5.9 + echo 3 + mount -t overlay overlay -o lowerdir=lower,workdir=work,upperdir=upper merged + mount -t overlay overlay -o lowerdir=lower2,workdir=work2,upperdir=upper2 merged2 + tar Jxvf linux-5.9.tar.xz -C merged + umount merged2 real 0m0.437s user 0m0.001s sys 0m0.001s + umount merged real 0m2.107s user 0m0.002s sys 0m0.090s + rm -rf upper/linux-5.9 + echo 3 + mount -t overlay overlay -o lowerdir=lower,workdir=work,upperdir=upper merged + mount -t overlay overlay -o lowerdir=lower2,workdir=work2,upperdir=upper2 merged2 + tar Jxvf linux-5.9.tar.xz -C merged + umount merged2 real 0m0.443s user 0m0.002s sys 0m0.001s + umount merged real 0m2.032s user 0m0.001s sys 0m0.105s + rm -rf upper/linux-5.9 + echo 3 + mount -t overlay overlay -o lowerdir=lower,workdir=work,upperdir=upper merged + mount -t overlay overlay -o lowerdir=lower2,workdir=work2,upperdir=upper2 merged2 + tar Jxvf linux-5.9.tar.xz -C merged + umount merged2 real 0m0.263s user 0m0.001s sys 0m0.001s + umount merged real 0m2.094s user 0m0.000s sys 0m0.083s [root@localhost o Thanks, Chengguang
