Re: Bizarre performance limitation

[Donald Lee <MacPPC2%caution.icompute.com@localhost>]

I don't think it's bizzarre at all.

Getting wire speed out of TCP is one thing.  Getting wire speed with NFS is
another.  There have been whole books written on this subject.

TCP params, including socket buffer sizes, NFS params (like TCP mounts),
NFS xfer sizes and client settings, write behind and other params on
the client all play a role.

Good luck. ;->

-dgl-

>Hi, all,
>
>I've used NetBSD-macppc extensively and still have many machines running it. 
>However, the last time I had a PowerMac G4 tower running NetBSD was quite a 
>long time ago (pre-NetBSD 4, I believe). At one point I had a tower saturating 
>a 100 Mbps Internet connection while serving video files via Apache, so I know 
>they can be quite fast.
>
>Recently I set up a Quicksilver tower with 1.5 gigs of memory, a 1.733 GHz 
>7448 accelerator, an ATTO UL3D 160 MB/sec UltraSCSI card, a 64 bit Intel 
>gigabit PCI card and NetBSD 5 so that I could do tape backups over the network 
>to an LTO-4 tape drive. However, it appears I cannot get more than 7 or 8 
>MB/sec tops through the network.
>
>The machine providing NFS shares is an 8 core Xserve running Mac OS X 10.6.2 
>with a direct gigabit connection. I've used the same machine with an amd64 
>system running NetBSD to do tape backups before, and I've been able to get at 
>minimun 30 MB/sec.
>
>I've tried using 9000 byte frames (no difference), adjusting the size of the 
>NFS transfers, using / not using hardware checksumming, and so on. The PowerPC 
>system is 85% or more idle with 2% interrupt and less than 15% system in top.
>
>The ethernet card is doing about 800-850 interrupts a second. With a 9000 byte 
>packet size and an 8k NFS transfer size, that makes for about 6.5 to 7 MB/sec 
>speed, which netstat bears out.
>
>Does anyone have any clue what might be so different between the macppc system 
>and an otherwise identical amd64 system which might explain the disparity?
>
>Thanks,
>John Klos