[Samba] CIFS client mounts meta ops 30 times slow than server

[Shenyue Chen]

Also from my observation, based on network packets and time measurements,
it seems the CIFS clients haven't done any sort of cache.

For example, doing a "ls" for 5 times on the same folder within a
short period of time. The network packet sizes are almost equal every time
and the time it takes is similar.

Isn't there supposed to be some page cache or dentry cache that could
accelerate this, under the loose cache policy? Or is this the expected
behavior?

Shenyue Chen <chensy1996 at gmail.com> 于2023年3月10日周五 01:15写道：

> Hi Samba users,
>
> We would like to use samba for re-exporting our other distributed file
> system (BeeGFS). However, we found that the meta data operations are very
> slow (dir stat, removal etc.). On SMB client the performance is more than
> 30x slow than on the SMB server. We would expect some slowness but this is
> too big a drop.
>
> This is the result on CIFS client
>
> $ sudo mdtest -b 10 -I 10 -L -z 2
>
> mdtest-3.3.0 was launched with 1 total task(s) on 1 node(s)
> Command line used: mdtest '-b' '10' '-I' '10' '-L' '-z' '2'
> FS: 1341.0 TiB   Used FS: 53.8%   Inodes: 0.0 Mi   Used Inodes: -nan%
>
> Nodemap: 1
> 1 tasks, 1000 files/directories
>
> SUMMARY rate: (of 1 iterations)
>    Operation                      Max            Min           Mean        Std Dev
>    ---------                      ---            ---           ----        -------
>    Directory creation        :          8.431          8.431          8.431          0.000
>    Directory stat            :         34.470         34.470         34.470          0.000
>    Directory removal         :         11.401         11.401         11.401          0.000
>    File creation             :         15.151         15.151         15.151          0.000
>    File stat                 :         26.313         26.313         26.313          0.000
>    File read                 :         11.206         11.206         11.206          0.000
>    File removal              :         10.526         10.526         10.526          0.000
>    Tree creation             :          9.121          9.121          9.121          0.000
>    Tree removal              :         15.190         15.190         15.190          0.000
> -- finished at 02/17/2023 10:11:41 --
>
> And this is the result of the same folder on SMB server.
>
> $ mdtest -b 10 -I 10 -L -z 2 -- started at 02/17/2023 10:26:11 --
> mdtest-3.3.0 was launched with 1 total task(s) on 1 node(s) Command line
> used: mdtest '-b' '10' '-I' '10' '-L' '-z' '2' FS: 1341.0 TiB Used FS:
> 54.0% Inodes: 0.0 Mi Used Inodes: -nan% Nodemap: 1 1 tasks, 1000
> files/directories SUMMARY rate: (of 1 iterations) Operation Max Min Mean
> Std Dev --------- --- --- ---- ------- Directory creation : 290.328 290.328
> 290.328 0.000 Directory stat : 702.193 702.193 702.193 0.000 Directory
> removal : 343.934 343.934 343.934 0.000 File creation : 330.556 330.556
> 330.556 0.000 File stat : 1368.871 1368.871 1368.871 0.000 File read :
> 519.276 519.276 519.276 0.000 File removal : 454.345 454.345 454.345 0.000
> Tree creation : 314.333 314.333 314.333 0.000 Tree removal : 382.234
> 382.234 382.234 0.000 -- finished at 02/17/2023 10:26:28 --
>
> Additionally, it seems our client does not have any kind of cache
> available. I've tried many options:
>
>    - cache=loose
>    - actimeo=3600
>    - nostrictsync
>    - noperm
>    - fsc
>    - etc....
>
> But none of the seems to have an impact.
>
> Our work load consists of mainly large number of small files.
>
> I know there many possible factors going on here. So I'm wondering if
> there is any way we could profile/trace this to tune the performance.
>
>
> Thanks!
>
> Info:
>
> Client linux kernel version: Ubuntu 22.04 5.15.0-60-generic
> Server SMB version: 4.15.13+dfsg-0ubuntu1
> Mount options: <path> type cifs
> (rw,relatime,vers=3.1.1,cache=strict,username=elvis_chen,uid=0,noforceuid,gid=0,noforcegid,addr=<ip>,file_mode=0755,dir_mode=0755,soft,nounix,serverino,mapposix,rsize=4194304,wsize=4194304,bsize=1048576,echo_interval=60,actimeo=1)
>