[Pvfs2-users] PVFS2 & Jumbo Frames

[Paulo Afonso Lopes]

Hi, all.

I have measured a 40% to 30% decrease in CPU use (Xeon 2.4G, 512k cache)
in IBM x335 with the mobo's Broadcom NIC (5703), at 80 MB/s (one port
only)by going to MTU 9000 instead of the std 1500 (kernel 2.4).

Some Bcom NICs do support jumbo, others (as the one in the HP DL145/G2,
Bcom 5721) do not. I have not played with interrupt coalescing, but it's
supposed to help a bit, too.

I did not know Bcom NICs had some offload capabilities; can you point out
where to look (or am I missing the point and you - Rob - are not using
Bcom?)

Regards,

paulo lopes


> Thanks - interesting document!
>
> --bob
>
> On Nov 2, 2006, at 11:37 AM, Robert Latham wrote:
>
>> On Thu, Nov 02, 2006 at 10:59:51AM -0600, Robert Olson wrote:
>>> The nodes in my cluster have dual Gig-E nics (tigon3). I'm pondering
>>> the installation of a second gigE switch to attach them all with a
>>> private storage network, and run it with jumbo frames. Do you think
>>> I'd see a significant performance increase with PVFS in this
>>> configuration?
>>
>> Hi Bob
>>
>> We definitely expect jumbo frames to help out pvfs a lot.  Ti's had
>> good results on the teragrid, for example [1].  Unfortunately, I don't
>> think anyone has quantified the benefit.
>>
>>> I'm also curious if folks have experimented with the effects of the
>>> TCP segment offload stuff that is available on these NICs.
>>
>> Again, should help PVFS a lot, but we've got no hard data.
>>
>> ==rob
>>
>> [1] http://www.teragridforum.org/mediawiki/index.php?title=TG-11
>>
>> --
>> Rob Latham
>> Mathematics and Computer Science Division    A215 0178 EA2D B059 8CDF
>> Argonne National Lab, IL USA                 B29D F333 664A 4280 315B
>>
>
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--
Paulo Afonso Lopes                        | Tel: +351- 21 294 8536
Departamento de Informática               | 294 8300 ext.10763
Faculdade de Ciências e Tecnologia        | Fax: +351- 21 294 8541
Universidade Nova de Lisboa               | e-mail: pal at di.fct.unl.pt
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