[stgt] [PATCH 2/2] use FIFO policy instead FILO for I/O thread request handling

FUJITA Tomonori fujita.tomonori at lab.ntt.co.jp
Mon Sep 14 14:01:55 CEST 2009

On Mon, 14 Sep 2009 11:46:37 +0300
Or Gerlitz <ogerlitz at voltaire.com> wrote:

> FUJITA Tomonori wrote:
> > Somehow, I/O threads perform requests in FILO manner. We should use FIFO for better performance
> Hi Tomo,
> Isn't LIFO processing being a NO NO for target that eventually provides 
> block device interface towards the initiator stack... so first and most, 
> this is a bug fix, thoughts?

It's not. tgt properly handles SCSI ordering rule.

The patch is about I/O threads policy. I/O threads simultaneously
performs multiple SCSI commands that can be performed in any order.

I/O threads uses FILO so if I/O threads has tons of requests, the
latency of the first request could be large.
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