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SubjectRe: [LKP] [lkp] [sctp] a6c2f79287: netperf.Throughput_Mbps -37.2% regression
On Wed, Aug 17, 2016 at 02:14:05PM +0800, Aaron Lu wrote:
> On Wed, Aug 17, 2016 at 01:41:04PM +0800, Xin Long wrote:
> > > The perf-profile data for the two commits are attached(for the case of
> > > prsctp_enable=1, the perf-profile data doesn't get collected for the 0
> > > case for some reason, I'm checking the problem now).
> > >
> > > The CPU gets much more idle time in the bisected commit a6c2f79287:
> > >
> > > 68.89% 0.70% [kernel.kallsyms] [k] entry_SYSCALL_64_fastpath
> > > 49.32% 0.12% [kernel.kallsyms] [k] sys_sendmsg
> > > 49.17% 0.12% [kernel.kallsyms] [k] __sys_sendmsg
> > > 48.58% 0.22% [kernel.kallsyms] [k] ___sys_sendmsg
> > > 46.69% 0.06% [kernel.kallsyms] [k] sock_sendmsg
> > > 46.31% 0.16% [kernel.kallsyms] [k] inet_sendmsg
> > > 45.90% 0.98% [kernel.kallsyms] [k] sctp_sendmsg
> > > 29.66% 0.45% [kernel.kallsyms] [k] sctp_do_sm
> > > 29.54% 0.23% [kernel.kallsyms] [k] cpu_startup_entry
> > > 28.81% 0.68% [kernel.kallsyms] [k] sctp_cmd_interpreter.isra.24
> > > 26.20% 0.00% [kernel.kallsyms] [k] start_secondary
> > > 23.04% 0.09% [kernel.kallsyms] [k] sctp_inq_push
> > > 23.03% 0.08% [kernel.kallsyms] [k] call_cpuidle
> > > 22.94% 0.00% [kernel.kallsyms] [k] cpuidle_enter
> > > 22.60% 0.18% [kernel.kallsyms] [k] cpuidle_enter_state
> > > 21.99% 21.99% [kernel.kallsyms] [k] intel_idle
> > > ... ...
> > >
> > > While its immediate parent commit 826d253d57 is mostly busy working:
> > >
> > > 98.53% 0.83% [kernel.kallsyms] [k] entry_SYSCALL_64_fastpath
> > > 78.13% 0.12% [kernel.kallsyms] [k] sys_sendmsg
> > > 78.03% 0.16% [kernel.kallsyms] [k] __sys_sendmsg
> > > 77.08% 0.28% [kernel.kallsyms] [k] ___sys_sendmsg
> > > 74.44% 0.08% [kernel.kallsyms] [k] sock_sendmsg
> > > 73.82% 0.13% [kernel.kallsyms] [k] inet_sendmsg
> > > 73.34% 1.44% [kernel.kallsyms] [k] sctp_sendmsg
> > > 47.52% 0.75% [kernel.kallsyms] [k] sctp_do_sm
> > > 46.19% 0.90% [kernel.kallsyms] [k] sctp_cmd_interpreter.isra.24
> > > 37.17% 1.43% [kernel.kallsyms] [k] sctp_outq_flush
> > > 36.93% 0.08% [kernel.kallsyms] [k] sctp_outq_uncork
> > > 34.24% 0.15% [kernel.kallsyms] [k] sctp_inq_push
> > > ... ...
> > > No idle related function above 1%.
> > >
> > > Will the bisected commit make the idle possible?
> > No, not at all. :)
> >
> > pls help to debug as I said in the last reply.
>
> OK, will see how to do that.
>
> In the meantime, I just tried to reproduce on my own desktop:
> Sandybridge i7-2600 CPU @ 3.40GHz and it reproduced:
> $ cat 4.7.0-rc6-01198-ga6c2f792873a/0/netperf.json
> {
> "netperf.Throughput_Mbps": [
> 752.9450000000002
> ]
> }
> $ cat 4.7.0-rc6-01197-g826d253d57b1/0/netperf.json
> {
> "netperf.Throughput_Mbps": [
> 1068.5556249999997
> ]
> }

On top of
commit 826d253d57b1 ("sctp: add SCTP_PR_ASSOC_STATUS on sctp sockopt")
I applied the below commit:

From 98dd2532b14e29dcc2ab40a7348755531afa79e4 Mon Sep 17 00:00:00 2001
From: Aaron Lu <aaron.lu@intel.com>
Date: Wed, 17 Aug 2016 14:20:00 +0800
Subject: [PATCH] sctp: test

---
include/net/sctp/structs.h | 3 +++
1 file changed, 3 insertions(+)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index d8e464aacb20..932f2780d3a4 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -602,6 +602,9 @@ struct sctp_chunk {
/* This needs to be recoverable for SCTP_SEND_FAILED events. */
struct sctp_sndrcvinfo sinfo;

+ unsigned long prsctp_param;
+ int sent_count;
+
/* Which association does this belong to? */
struct sctp_association *asoc;

--
2.5.5
Then the performance dropped to the same as the bisected commit
a6c2f792873a:
$ cat 4.7.0-rc6-01198-g98dd2532b14e/0/netperf.json
{
"netperf.Throughput_Mbps": [
754.494375
]
}
I think this agrees with the perf data in that the newly added function
doesn't show up in the perf-profile but still, the performance drops.
So the only possible reason is the newly added fields to the sctp_chunk
structure.

Is this expected?

Thanks,
Aaron

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