Quick Edit and iowait

[anewday]

Ok, I don't stream any media files on the server. Max I/O is set to 150M, it should be enough for a forum withi media downloads? The ethernet port is 100Mbit.

 

[mistwang]

I/O Buffer is only for PHP request/response, won't affect media files, unless the media files were sent through PHP. Does it work better with larger I/O buffer today?

 

[anewday]

Can't notice any difference I have tried 150M and 200M. Another observation is that posting messages for the first time doesn't cause any high iowait isues. It's just subsequent edits that do. Very strange...

 

[mistwang]

I think probably know what is going on. LSWS use on-disk buffer to store the body of large post requests. this will cause high I/O wait.
The solution is to change the swapping directory to use /dev/shm instead of /tmp/lshttpd/swap.
http://www.litespeedtech.com/docs/webserver/config/general/#swappingDir

 

[anewday]

I think probably know what is going on. LSWS use on-disk buffer to store the body of large post requests. this will cause high I/O wait.
The solution is to change the swapping directory to use /dev/shm instead of /tmp/lshttpd/swap.
http://www.litespeedtech.com/docs/webserver/config/general/#swappingDir

Ok, I will try it later. But some posts I edit contain less than 10 letters.

 

[furimedia]

I think I also have this problem.
My server was always usually less than 1 but now it just averages 1 and higher.

What does setting to /dev/shm do? I am guessing it will uses System RAM instead of accessing disk and if this is the case, shouldn't using /dev/shm be the default behaviour for maximum performance?

 

[anewday]

That's what I want to know too. Also, if Memory I/O Buffer is not full (as in my case) then how would setting the path to /dev/shm help since it doesn't have a need for it. Please clarify.

 

[mistwang]

We use on disk buffer mainly for buffering the large request body for those site dealing with large media files, let a 600MB media file fill up the memory is not a good idea, and there could be 20 upload sessions at the same time.

Let's see what we can do about it. At least we can set the threshold higher when there are enough free memory.

 

[anewday]

George, so setting the swapping directory to /dev/shm is useless since my Memory I/O Buffer is not full, right? I don't stream any media files by php, either.

 

[mistwang]

No, it should help. as current LSWS release use 1MB as the threshold on whether to use the on disk buffer.
When a request has a request body larger than the threshold, the on disk buffer will be used no matter the memory I/O buffer is full or not.

We will change it to 10MB in 3.3.11 release.

 

[anewday]

Ok, sounds good. Should include the threshold value on the tooltip in web console. Maybe even allow user to define it. Thanks!

 

[miracle]

10MB is more than enough in most cases? Why not make LSWS uses as much memory as possible, instead of use disk buffer?

 

[anewday]

Quick/regular edit and moving topics still causes high iowait occassionally in 3.3.11 Do you think it's good to disable mysql persistent connections in php.ini ?

 

[anewday]

2008-04-26 10:52:22.678	INFO	[AdminPHP] pid list size: 1
2008-04-26 10:52:22.678	INFO	[AdminPHP] add child process pid: 7016

This shows up in the error_log file whenever the load spikes due to iowait. hmmmm.

How to lessen those on the error_log file?

 

[mistwang]

2008-04-26 10:52:22.678    INFO    [AdminPHP] pid list size: 1
2008-04-26 10:52:22.678    INFO    [AdminPHP] add child process pid: 7016

This shows up in the error_log file whenever the load spikes due to iowait. hmmmm.

How to lessen those on the error_log file?

That's just because you are using the Admin console.

 

[mistwang]

Quick/regular edit and moving topics still causes high iowait occassionally in 3.3.11 Do you think it's good to disable mysql persistent connections in php.ini ?

does not matter.

 

[anewday]

That's just because you are using the Admin console.

I wasn't using the Admin Console during the timestamps though.