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SubjectRe: [RFC] x86,perf: Implement minimal P4 PMU driver v14

* Cyrill Gorcunov <gorcunov@openvz.org> wrote:

> x86,perf: Implement minimal P4 PMU driver v15

tried it on a Pentium-D dual core CPU, and it boots fine:

[ 0.020009] using mwait in idle threads.
[ 0.021004] Performance Events: Netburst events, Netburst P4/Xeon PMU driver.
[ 0.024006] ... version: 0
[ 0.025003] ... bit width: 40
[ 0.026003] ... generic registers: 18
[ 0.027003] ... value mask: 000000ffffffffff
[ 0.028003] ... max period: 0000007fffffffff
[ 0.029003] ... fixed-purpose events: 0
[ 0.030003] ... event mask: 000000000003ffff
[ 0.031027] ACPI: Core revision 20100121
[ 0.050126] Setting APIC routing to flat
[ 0.051010] enabled ExtINT on CPU#0

perf stat seems to work fine as well:

rhea:~> perf stat ls >/dev/null

Performance counter stats for 'ls':

6.596037 task-clock-msecs # 0.439 CPUs
1 context-switches # 0.000 M/sec
0 CPU-migrations # 0.000 M/sec
236 page-faults # 0.036 M/sec
4745843 cycles # 719.499 M/sec
0 instructions # 0.000 IPC
<not counted> cache-references
<not counted> cache-misses

0.015009286 seconds time elapsed

perf top works fine as well:

------------------------------------------------------------------------------
PerfTop: 25056 irqs/sec kernel:25.7% [100000 cycles], (all, 2 CPUs)
------------------------------------------------------------------------------

samples pcnt kernel function
_______ _____ _______________

845.00 - 6.6% : __switch_to
785.00 - 6.1% : schedule
687.00 - 5.3% : perf_poll
455.00 - 3.5% : _raw_spin_lock_irqsave
436.00 - 3.4% : delay_tsc
371.00 - 2.9% : fget_light
346.00 - 2.7% : pick_next_task_fair
328.00 - 2.5% : fput
285.00 - 2.2% : free_poll_entry

i also triggered this:

[ 436.224139] PMU: Dep events are not implemented yet

i'm getting a healthy amount of NMIs:

NMI: 44400 108796 Non-maskable interrupts

perf record + report works fine too:

# Samples: 32829281626
#
# Overhead Command Shared Object Symbol
# ........ ............... .................. ......
#
11.22% pipe-test-1m [kernel.kallsyms] [k] __switch_to
4.82% pipe-test-1m [kernel.kallsyms] [k] switch_mm
4.37% pipe-test-1m [kernel.kallsyms] [k] schedule
3.01% pipe-test-1m [kernel.kallsyms] [k] pipe_read
2.96% pipe-test-1m [kernel.kallsyms] [k] system_call
2.53% pipe-test-1m [kernel.kallsyms] [k] update_curr
2.15% pipe-test-1m [kernel.kallsyms] [k] vfs_read

perf annotate __switch_to works too, and sees inside irqs-disabled regions due
to NMI sampling:

0.00 : ffffffff81001664: 48 89 c2 mov %rax,%rdx
0.18 : ffffffff81001667: b9 00 01 00 c0 mov $0xc0000100,%ecx
0.00 : ffffffff8100166c: 48 c1 ea 20 shr $0x20,%rdx
0.00 : ffffffff81001670: 0f 30 wrmsr
67.80 : ffffffff81001672: 45 85 ff test %r15d,%r15d
1.85 : ffffffff81001675: 66 89 b3 8c 04 00 00 mov %si,0x48c(%rbx)
5.35 : ffffffff8100167c: 41 0f b7 bd 8e 04 00 movzwl 0x48e(%r13),%edi
0.00 : ffffffff81001683: 00

(and that wrmsr is indeed one known overhead point in __switch_to.)

All in one, the P4 PMU perf driver works on this box like a charm and all the
common profiling workflows work out of box, without any serious limitations -
really nice work! (Obviously some events wont work yet, etc.)

So it's pretty impressive and i've queued up your patch in tip:perf/x86 and
will merge it into perf/core after others had a chance to test it too.

Ingo


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