Date: Tue, 9 Mar 2010 14:12:40 -0800 From: Pyun YongHyeon <pyunyh@gmail.com> To: Ian FREISLICH <ianf@clue.co.za> Cc: current@freebsd.org Subject: Re: dev.bce.X.com_no_buffers increasing and packet loss Message-ID: <20100309221240.GR1311@michelle.cdnetworks.com> In-Reply-To: <E1Np7Ok-000Gpl-FE@clue.co.za> References: <20100305210435.GF14818@michelle.cdnetworks.com> <20100305184046.GD14818@michelle.cdnetworks.com> <20100305175639.GB14818@michelle.cdnetworks.com> <E1NnVaT-0003Ft-3p@clue.co.za> <E1Nnc4d-0003mB-6e@clue.co.za> <E1Nne0Q-0003uZ-OR@clue.co.za> <E1Nnesz-00040L-AQ@clue.co.za> <E1NoeCu-0006P9-12@clue.co.za> <E1NozXP-000GGH-T9@clue.co.za> <E1Np7Ok-000Gpl-FE@clue.co.za>
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On Tue, Mar 09, 2010 at 11:55:30PM +0200, Ian FREISLICH wrote: > Pyun YongHyeon wrote: > > On Tue, Mar 09, 2010 at 03:31:55PM +0200, Ian FREISLICH wrote: > > > Can you explain the tunables please - I'm guessing it's these: > > I think I asked the wrong question. What is a "Quick BD Chain"? I don't know why Broadocom uses 'Quick'. It's a just buffer descriptor chain for TX/RX. > What relation should this number have to traffic rate. Is there a > maximum and what are reasonable numbers for setting this to? > The maximum BD chain would be number of configured TX/RX descriptors. And 1 would be minimum value as you have to want to get status block for each TX/RX. Finding best value may depend on specific load. > I set the RX as high as 512 in 64 quanta but it made little difference > to the interrupt rate. At times where we experience the packet > loss and com_no_buffers increases, the interrupt rate on between 1 > and 3 of the 4 bce interfaces fell from about 3200/s to 130/s. > BD chain is just one of parameters. bce(4) controllers also provide more advanced features that fine control interrupt moderation(TX/RX ticks). It's hard to explain all the details so you may want to read public data sheet of bce(4). http://www.broadcom.com/collateral/pg/NetXtremeII-PG203-R.pdf See host coalescing registers(page 484). > We're wondering if the switches we're using could be causing this > problem - they're Dell PowerConnect 5448. I've seen complaints of > random packet loss caused by these switches on the Internet. We > have some new H3C 5100 series switches which we're planning on > swapping for the Dells tomorrow to see if it makes a difference. > Not sure but it does not explain increasing dev.bce.X.com_no_buffers counter. > Ian > > -- > Ian Freislich
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