Re: [dm-devel] Thoughts on removing the remap cache

[FUJITA Tomonori <fujita tomonori lab ntt co jp>]

From: Dan Smith <danms us ibm com>
Subject: Re: [dm-devel] Thoughts on removing the remap cache
Date: Sat, 30 Sep 2006 08:44:26 -0700

> FT> I guess that dbench generates relatively large size I/Os than
> FT> common workloads, which is more sensitive to latency.
> 
> Right, that is what I am thinking.  However, dbench inside a domU does
> not perform well either.  Even running dbench inside a domU, the
> batches that the userspace daemon sees are only about 10 requests,
> compared to several thousand at times when running on bare metal.
> 
> FT> Seems that Xen camp is pretty happy with blktap. So dm-userspace
> FT> should be ok with domU. Maybe it's time to try ring buffer stuff
> FT> again. :)
> 
> You think that the ring buffer has the potential to be lower latency
> due to fewer memcpy()'s right?

Yeah, though there might be other factors, I guess.

Anyway, could you try the new ring buffer patch that I posted?