systems without pread?
James Peach
jpeach at sgi.com
Tue Dec 16 22:30:22 GMT 2003
On Tue, 16 Dec 2003 10:15:05 -0800
Jeremy Allison <jra at samba.org> wrote:
> On Tue, Dec 16, 2003 at 01:19:48PM +1100, James Peach wrote:
> > Hi all,
> >
> > I have been testing a patch which adds pread/pwrite oerations to the
> > Samba VFS layer and makes exclusive use of them in the file I/O path.
> > The current version emulates p{read,write} using
> > lseek/lseek/{read,write}/lseek if they are absent. So while it is a big
> > performance win for the lucky platforms_with_ those APIs, it does
> > introduce suckage for those without.
>
> Hmmmm. How have you tested this performance win ?
I have a smallish test setup using an Origin 3k server and 4 Origin 300
clients. I'm connecting each client to the server through a different gig-e
NIC and running multiple load generators on each client. I'm gathering
performance numbers using Performance Co-Pilot - these include NIC throughput,
CPU time, samba IOPs per second, and a bunch more stuff.
Despite my previous assurance, I'm not able to publish the full set of
numbers, but here is a small selection that shows the most significant
improvements:
threads smbd.smb_count network.interface.bytes
(in) / (out)
Without pread:
12 9262.938 11.87 / 16.67 (netbench)
8192 12 8902.365 1.56 / 73.63 (reads)
8192 12 7814.518 64.90 / 1.22 (writes)
With pread:
12 11563.115 14.82 / 20.93 (netbench)
8192 12 16288.886 2.83 / 134.88 (reads)
8192 12 16487.643 137.19 / 2.57 (writes)
----- -- --------- ---------------
^ ^ ^ ^
| | | total avg. thoughput (MiB/s)
| | - SMB count (from samba profiling counts)
| - # workloads per client
- I/O block size
> I like the look of these changes but I'd want to make sure it really
> helped on significant platforms (Linux for example).
The basic effect of the patch is to reduce server latency, which has a big
effect. In my testing, the numbers for the pread patch are roughly equivalent
to those of using tdb spinlocks, so it should help anyone who finds spinlocks
helpful.
--
James Peach | jpeach at sgi.com | SGI Australian Software Group
I don't speak for SGI.
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