2005-04-19 15:46:13

by Francesco Oppedisano

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Subject: more packets than interrupts

Hi,
using tcpdump to capture ethernet packets i noticed i obtain more
packets than interrupts (taken from /proc/interrupts).
I found this with all NICs available to me (8139, e1000pro, one using
sk98lin, 3com 59x, via rhine etc..).
Where the NIC supports any type of mitigation or similar (see NAPI),
this function are disabled: so this happens with no mitigation
mechanisms.
How can this happen?
Can every driver manage many packets per call?

Thank you very much
Francesco


2005-04-19 18:34:49

by David Miller

[permalink] [raw]
Subject: Re: more packets than interrupts

On Tue, 19 Apr 2005 15:46:07 +0000
Francesco Oppedisano <[email protected]> wrote:
> Can every driver manage many packets per call?

Most can. If more packets arrive between between when the chip
signals the interrupt and the cpu actually gets to the driver
interrupt handler, multiple packets per interrupt can easily happen.