What is juicefs doing with fuse and meta engine per second.

[OrvilleQ]

Hello there.

I realized juicefs operates a fuse thing and a database thing per second. I'm trying to migrate my meta engine to a serverless request based pricing model so this will make my database fee even much higher.

So what are this operations and is it possible to disable or extend the cycle they operate?

[OrvilleQ]

After some research I thought it is controlled by --attr-cache value, --entry-cache value and --dir-entry-cache value. I set them to 60 then but juicefs still do a metadata thing per 10 second.

------usage------ ----------fuse--------- ----meta--- -blockcache ---object--
 cpu   mem   buf | ops   lat   read write| ops   lat | read write| get   put 
 0.0%   57M    0 |   0     0     0     0 |   0     0 |   0     0 |   0     0 
 0.7%   58M    0 |  10  0.30     0     0 |   0     0 |   0     0 |   0     0 
 0.7%   58M    0 |  10  0.24     0     0 |   0     0 |   0     0 |   0     0 
 0.8%   58M    0 |  10  0.18     0     0 |   1  20.0 |   0     0 |   0     0 
 0.6%   58M    0 |  10  0.21     0     0 |   0     0 |   0     0 |   0     0 
 0.8%   59M    0 |  10  0.18     0     0 |   0     0 |   0     0 |   0     0 
 0.4%   59M    0 |  10  0.20     0     0 |   0     0 |   0     0 |   0     0 
 0.9%   59M    0 |  10  0.27     0     0 |   0     0 |   0     0 |   0     0 
 0.6%   59M    0 |  10  0.23     0     0 |   0     0 |   0     0 |   0     0 
 0.6%   59M    0 |  10  0.14     0     0 |   0     0 |   0     0 |   0     0 
 0.8%   60M    0 |  10  0.18     0     0 |   0     0 |   0     0 |   0     0 
 0.8%   60M    0 |  10  0.75     0     0 |   0     0 |   0     0 |   0     0 
 0.9%   60M    0 |  10  0.37     0     0 |   0     0 |   0     0 |   0     0 
 1.1%   60M    0 |  10  0.24     0     0 |   1  20.0 |   0     0 |   0     0 
 0.7%   61M    0 |  10  0.20     0     0 |   0     0 |   0     0 |   0     0 
 0.8%   61M    0 |  10  0.17     0     0 |   0     0 |   0     0 |   0     0 
 0.5%   61M    0 |  10  0.17     0     0 |   0     0 |   0     0 |   0     0 
 0.6%   61M    0 |  10  0.16     0     0 |   0     0 |   0     0 |   0     0 
 0.9%   62M    0 |  10  0.21     0     0 |   0     0 |   0     0 |   0     0 
 2.0%   62M    0 |  10  0.37     0     0 |   0     0 |   0     0 |   0     0 
 0.7%   62M    0 |  10  0.19     0     0 |   0     0 |   0     0 |   0     0 
 0.8%   62M    0 |  10  0.20     0     0 |   0     0 |   0     0 |   0     0 
 1.0%   62M    0 |  10  0.21     0     0 |   0     0 |   0     0 |   0     0 
 1.0%   62M    0 |  10  0.24     0     0 |   1  20.6 |   0     0 |   0     0 
 0.6%   62M    0 |  10  0.24     0     0 |   0     0 |   0     0 |   0     0 
 0.8%   62M    0 |  10  0.19     0     0 |   0     0 |   0     0 |   0     0 
 0.8%   62M    0 |  10  0.20     0     0 |   0     0 |   0     0 |   0     0 
 0.9%   62M    0 |  10  0.29     0     0 |   0     0 |   0     0 |   0     0 
 1.0%   62M    0 |  10  0.20     0     0 |   0     0 |   0     0 |   0     0 
 0.7%   62M    0 |  10  0.26     0     0 |   0     0 |   0     0 |   0     0

Then I tried --heartbeat and --open-cache, but nothing helped, and I can't find out what is juicefs doing though debug mode too.

Could anyone help me with that?

Thank you.

[qingyunha]

juicefs stats open .stats file every interval, It may be relevent.

[xiaogaozi]

You can view the Access Log of JuiceFS to learn what happened.

[SandyXSD]

The system repeatedly calls statfs to update usage of mounted file system, which will send read request to meta engine. Meanwhile, JuiceFS session has to refresh itself to update its expire timestamp, which will send write request to metadata engine.