2007-12-27 02:34:29

by Jeff Garzik

[permalink] [raw]
Subject: Re: read-ahead in NFS server

saeed bishara wrote:
> Hi,
> my NFS server seems not to utilize the read-ahead feature, my exported
> dir is located on ext3 fs over sata disk. the sata controller can
> issue commands up to 1MB, also I modified the read ahead under the sys
> to 1MB. but when the client do reads in 32KB chunks (rsize), I can see
> in the server side that all IOs are ~32KB. my kernel version is
> 2.6.22.7.
> according to the nfsd code, the NFS server should utilize the
> read-ahead feature, but what should I do
> to make it work?

(linux-nfs added to cc)

I cannot speak for the NFS server code specifically, but 32kb sounds
like a network read (or write) data size limit.

Are you using TCP? Are you using NFSv4, or an older version?

Jeff




2007-12-27 08:50:08

by saeed bishara

[permalink] [raw]
Subject: Re: read-ahead in NFS server

> (linux-nfs added to cc)
>
> I cannot speak for the NFS server code specifically, but 32kb sounds
> like a network read (or write) data size limit.
yes
>
> Are you using TCP? Are you using NFSv4, or an older version?
I'm using NFSv3/UDP.
I found that the actual requests size was 16KB, after doing some hacks
in server&client I managed to make it 60KB, now I see better
performance, and I see that the average request size is ~130KB which
means that there is actually read-ahead. but why it's only 130KB? how
can I make it larger?
when I run local dd with bs=4K, I can see that the average IO size is
more than 300KB.