linux-kernel - x86 perf's dTLB-load-misses broken on IvyBridge?

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Date:	Tue, 18 Feb 2014 15:11:59 -0800
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	Andi Kleen <ak@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: x86 perf's dTLB-load-misses broken on IvyBridge?

I noticed that perf's dTLB-load-misses even t isn't working on my
Ivybridge system:

>  Performance counter stats for 'system wide':
> 
>                  0      dTLB-load-misses                                             [100.00%]
>             48,570      dTLB-store-misses                                            [100.00%]
>            202,573      iTLB-loads                                                   [100.00%]
>            271,546      iTLB-load-misses          #  134.05% of all iTLB cache hits 

But it works on a SandyBridge system that I have.

arch/x86/kernel/cpu/perf_event_intel.c seems to use the same tables for
SandyBridge and IvyBridge, so they both use the
'MEM_UOP_RETIRED.ALL_LOADS' event:

>  [ C(DTLB) ] = {
>         [ C(OP_READ) ] = {
>                 [ C(RESULT_ACCESS) ] = 0x81d0, /* MEM_UOP_RETIRED.ALL_LOADS */
>                 [ C(RESULT_MISS)   ] = 0x0108, /* DTLB_LOAD_MISSES.CAUSES_A_WALK */
>         },

But that event looks to be unsupported on this CPU:

> /ocperf.py stat -a -e mem_uops_retired.all_loads sleep 1
> perf stat -a -e cpu/event=0xd0,umask=0x81,name=mem_uops_retired_all_loads/ sleep 1
> 
>  Performance counter stats for 'system wide':
> 
>    <not supported>      mem_uops_retired_all_loads
>         50,204,763      mem_uops_retired_all_loads_ps

But there's a "_ps" version which uses PEBS which does work?

>   mem_uops_retired.all_loads                  [Load uops retired to architected path with filter on bits 0 and 1 applied. (Supports PEBS)]
>   mem_uops_retired.all_loads_ps               [Load uops retired to architected path with filter on bits 0 and 1 applied.  (Uses PEBS) (Uses PEBS)]

Should we swap perf_event_intel.c over to use the PEBS version so that
it works everywhere?
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