qlge uses an irq enable/disable refcounting scheme that is:
* poorly implemented
Uses a spin_lock to protect accesses to the irq_cnt atomic
variable.
* buggy
Breaks when there is not a 1:1 sequence of irq - napi_poll, such as
when using SO_BUSY_POLL.
* unnecessary
The purpose or irq_cnt is to reduce irq control writes when
multiple work items result from one irq: the irq is re-enabled
after all work is done.
Analysis of the irq handler shows that there is only one case where
there might be two workers scheduled at once, and those have
separate irq masking bits.
Therefore, remove irq_cnt.
Additionally, we get a performance improvement:
perf stat -e cycles -a -r5 super_netperf 100 -H 192.168.33.1 -t TCP_RR
Before:
628560
628056
622103
622744
627202
[...]
268,803,947,669 cycles ( +- 0.09% )
After:
636300
634106
634984
638555
634188
[...]
259,237,291,449 cycles ( +- 0.19% )
Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Link: https://lore.kernel.org/r/20190927101210.23856-3-bpoirier@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
e759b5cf70