Module Name: src
Committed By: msaitoh
Date: Wed Mar 27 03:29:50 UTC 2019
Modified Files:
src/sys/dev/pci: if_bnx.c
Log Message:
Apply OpenBSD rev. 1.94:
> ido not disable interrupts in the isr and then enable them again
> when leaving. when you're handling an interrupt it is masked.
> whacking the chip is work for no gain.
>
> modify the interrupt handler so it only processes the rings once
> rather than looping over them until it runs out of work to do
>
> looping in the isr is bad for several reasons:
>
> firstly, the chip does interrupt mitigation so you have a
> decent/predictable amount of work to do in the isr. your first loop
> will do that chunk of work (ie, it pulls off 50ish packets), and
> then the successive looping aggressively pull one or two packets
> off the rx ring. these extra loops work against the benefit that
> interrupt mitigation provides.
>
> bus space reads are slow. we should avoid doing them where possible
> (but we should always do them when necessary).
>
> doing the loop 5 times per isr works against the mclgeti semantics.
> it knows a nic is busy and therefore needs more rx descriptors by
> watching to see when the nic uses all of its descriptors between
> interrupts. if we're aggressively pulling packets off by looping
> in the isr then we're skewing this check.
>
> ok deraadt@
To generate a diff of this commit:
cvs rdiff -u -r1.69 -r1.70 src/sys/dev/pci/if_bnx.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
