On 04.07.2012 00:27, Luigi Rizzo wrote:
On Tue, Jul 03, 2012 at 09:37:38PM +0400, Alexander V. Chernikov wrote:
...
Thanks, another good point. I forgot to merge this option from andre's
patch.
Another 30-40-50kpps to win.
not much gain though.
What about the other IPSTAT_INC counters ?
Well, we should then remove all such counters (total, forwarded) and
per-interface statistics (at least for forwarded packets).
I think the IPSTAT_INC macros were introduced (by rwatson ?)
following a discussion on how to make the counters per-cpu
and avoid the contention on cache lines.
But they are still implemented as a single instance,
and neither volatile nor atomic, so it is not even clear
that they can give reliable results, let alone the fact
that you are likely to get some cache misses.
the relevant macro is in ip_var.h.
Hm. This seems to be just per-vnet structure instance.
We've got some more real DPCPU stuff (sys/pcpu.h && kern/subr_pcpu.c)
which can be used for global ipstat structure, however since it is
allocated from single area without possibility to free we can't use it
for per-interface counters.
I'll try to run tests without any possibly contested counters and report
the results on Thursday.
Cheers
luigi
+u_int rt_count = 1;
+SYSCTL_INT(_net, OID_AUTO, rt_count, CTLFLAG_RW,&rt_count, 1, "");
@@ -601,17 +625,20 @@ passout:
if (error != 0)
IPSTAT_INC(ips_odropped);
else {
- ro.ro_rt->rt_rmx.rmx_pksent++;
+ if (rt_count)
+ ro.ro_rt->rt_rmx.rmx_pksent++;
IPSTAT_INC(ips_forward);
IPSTAT_INC(ips_fastforward);
cheers
luigi
--
WBR, Alexander
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--
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