Re: [Lse-tech] Re: [RFC][PATCH] Scalable FD Management using Read-Copy-Update

From: Maneesh Soni (
Date: Thu Apr 12 2001 - 10:43:54 EST

On Wed, Apr 11, 2001 at 06:29:30PM -0700, Anton Blanchard wrote:
> > This patch provides a very good performance improvement in file
> > descriptor management for SMP linux kernel on a 4-way machine with the
> > expectation of even higher gains on higher end machines. The patch uses the
> > read-copy-update mechanism for Linux, published earlier at the sourceforge
> > site under Linux Scalablity Effort project.
> >
> Good stuff!
> It would be interesting to try a filesystem benchmark such as dbench. On
> a quad PPC fget was chewing up more than its fair share of cpu time.
> Anton

Hello Anton,

Thank you for your suggestion. I tried dbench for on a 4-way PIII Xeon box, with
1MB L2 Cache and 1GB of RAM. I ran it on 8 GB ext2 partition with Adaptec 7896
SCSI controller. I ran "dbench 100" and "dbench 200" for five times and took the
average of the throughput and found that for

Base (2.4.2) -
        100 Average Throughput = 39.628 MB/sec
        200 Average Throughput = 22.792 MB/sec

Base + files_struct patch -
        100 Average Throughput = 39.874 MB/sec
        200 Average Throughput = 23.174 MB/sec
I found this value quite less than the one present in the README distributed
with dbench tarball. I think the numbers in the README were for a similar
machine but with 2.2.9 kernel.

As you can see the performance with files_struct patch is almost same as base.
I feel I am hitting some bottleneck other than fget() in both base and the
patched versions. I think atleast for base version I should get similar numbers
as mentions in the README for similar configuration. Though I intend to do some
profiling to look into this but it will be helpfull if you can tell me if there
is some known thing regarding this.

I am copying this to Andrew also, if he can also help. Also if you have some
dbench numbers from 2.4.x kernel, please let me have a look into those also.

Thank you,

Maneesh Soni <>
IBM Linux Technology Center,
IBM Software Lab, Bangalore, India
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