Re: 2.5.38-mm2

From: Jens Axboe (
Date: Mon Sep 23 2002 - 02:16:33 EST

On Sun, Sep 22 2002, Andrew Morton wrote:
> +read-latency.patch
> Fix the writer-starves-reader elevator problem. This is basically
> the read_latency2 patch from -ac kernels.
> On IDE it provides a 100x improvement in read throughput when there
> is heavy writeback happening. 40x on SCSI. You need to disable

Ah interesting. I do still think that it is worth to investigate _why_
both elevator_linus and deadline does not prevent the read starvation.
The read-latency is a hack, not a solution imo.

> tagged command queueing on scsi - it appears to be quite stupidly
> implemented.

Ahem I think you are being excessively harsh, or maybe passing judgement
on something you haven't even looked at. Did you consider that you
_drive_ may be the broken component? Excessive turn-around times for
request when using deep tcq is not unusual, by far.

Jens Axboe

- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to More majordomo info at Please read the FAQ at

This archive was generated by hypermail 2b29 : Mon Sep 23 2002 - 22:00:38 EST