Re: [Scst-devel] Dynamic IO Flow control

[Bart V. A. <bar...@sa...>]

On 01/20/15 23:47, Rakesh Patel wrote:
> To implement simple dynamic IO flow control, following parameters are
> required.
> 
> 1) SCST command timeout.
> 2) SCST device queue depth.
> 3) SCST command execution time.
> 
> If command execution time is > timeout/5, then new queue depth is max
> (1, cur_queue_depth/2).
> 
> If command execution time is < timeout/10, then new queue depth is
> min(MAX_DEPTH, curr_queue_depth + 1).
> 
> How go get and set these parameters? 
> 
> Are there any SYSFS variables available for these parameters? 
> 
> Are there any implementation done regarding "dynamic IO flow control".

Hello Rakesh,

Do you want to implement dynamic flow control at the initiator side or
at the target side ? If you would like to implement this at the
initiator side, are you aware that it is possible to implement dynamic
flow control without knowing parameters 1-3 ? See e.g.
scsi_track_queue_full() in drivers/scsi/scsi.c in the Linux kernel.

Bart.