Re: [PATCH] 2.5.21 IDE 91

From: Jens Axboe (
Date: Sat Jun 15 2002 - 12:17:11 EST

On Sat, Jun 15 2002, wrote:
> > One possibile culprit here is the doubling of the request queue size
> > in 2.5.20. A long time ago it was 1024 slots. Then it went to
> > 128. That's where it is in Marcelo kernels. Then -ac kernels
> > went up to 1024 because they have read-latency2. Somehow 2.5 found
> > itself at 256 slots. In 2.5.20 it slealthily snuck up to 512
> > slots. I didn't squeak about this because I was interested to see what
> > effect it would have.
> Interesting. I've seen read-latency2 drop dbench throughput in -aa
> kernels (but I use it anyway). I'd like to capture the request
> queue size. Is there a command or file in /proc that displays
> it, or should I just grep drivers/block/ll_rw_blk.c?

There is currently no way you can capture the queue request state. In
the past I've done sysrq hacks to display it, but that's about it.

Jens Axboe

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