em driver input errors

[rihad at mail.ru]

-- Stanislav Sedov wrote : 
On Wed, 5 Aug 2009 00:30:20 -0700 (PDT)
alexpalias-bsdstable at yaho... mentioned:

>> dev.em.0.rx_processing_limit=300
>> dev.em.1.rx_processing_limit=300
>> dev.em.2.rx_processing_limit=300
>> dev.em.3.rx_processing_limit=300

> This tunables only affects polling mode.  Do you use polling with this
> adapters or just standard interrupt-based mode?

Why? In if_em.c, em_rxeof() is used both in legacy polling and in fast-interrupts / MSIX interrupts modes.
I have the same problem of many Ierrs on input on em0 at a load of 500-600 mbps, and increasing rx_processing_limit (or setting it to -1) doesn't help at all.

em0: Receive No Buffers = 4442943
em0: RX overruns = 83367

Next thing I'll try will be hw.em.rxd=4096.

I don't think polling would help as it is not the interrupt load causing the drops (as evidenced by top -HS), but rather insufficiently large input buffers.

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