Re: [PATCH net-next] tcp: avoid expensive pskb_expand_head() calls

Eric Dumazet
2012-04-18T17:40:55Z

On Wed, 2012-04-18 at 10:30 -0700, Rick Jones wrote:

> I was thinking more about the race if any between the ACK for the last
> byte of the 64 KB skb and the transmit completion processing freeing it
> in the driver. But that may be moot.
>

No race, its done with atomic operations.

> >
> > # perf stat -r 5 -d -d -o RES.before taskset 1 netperf -H 192.168.99.1 -l 20
>
> I'm still learning about perf, and the manpage I have for it does not
> discuss the -d option but is that doing system wide, or only in the
> context of the netperf process?

In fact I used -a option and forgot to copy it in the mail I sent

perf stat -h

usage: perf stat [<options>] [<command>]

-e, --event <event> event selector. use 'perf list' to list available events
--filter <filter>
event filter
-i, --no-inherit child tasks do not inherit counters
-p, --pid <pid> stat events on existing process id
-t, --tid <tid> stat events on existing thread id
-a, --all-cpus system-wide collection from all CPUs
-g, --group put the counters into a counter group
-c, --scale scale/normalize counters
-v, --verbose be more verbose (show counter open errors, etc)
-r, --repeat <n> repeat command and print average + stddev (max: 100)
-n, --null null run - dont start any counters
-d, --detailed detailed run - start a lot of events
-S, --sync call sync() before starting a run
-B, --big-num print large numbers with thousands' separators
-C, --cpu <cpu> list of cpus to monitor in system-wide
-A, --no-aggr disable CPU count aggregation
-x, --field-separator <separator>
print counts with custom separator
-G, --cgroup <name> monitor event in cgroup name only
-o, --output <file> output file name
--append append to the output file
--log-fd <n> log output to fd, instead of stderr