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Date:   Thu, 6 Jun 2019 09:05:16 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v2 0/7] perf diff: diff cycles at basic block level



On 6/5/2019 7:44 PM, Jiri Olsa wrote:
> On Mon, Jun 03, 2019 at 10:36:10PM +0800, Jin Yao wrote:
>> In some cases small changes in hot loops can show big differences.
>> But it's difficult to identify these differences.
>>
>> perf diff currently can only diff symbols (functions). We can also expand
>> it to diff cycles of individual programs blocks as reported by timed LBR.
>> This would allow to identify changes in specific code accurately.
> 
> can't compile on Fedora 30
> 
> builtin-diff.c: In function ‘block_cycles_diff_cmp’:
> builtin-diff.c:544:6: error: absolute value function ‘abs’ given an argument of type ‘s64’ {aka ‘long int’} but has parameter of type ‘int’ which may cause truncation of value [-Werror=absolute-value]
>    544 |  l = abs(left->diff.cycles);
>        |      ^~~
> builtin-diff.c:545:6: error: absolute value function ‘abs’ given an argument of type ‘s64’ {aka ‘long int’} but has parameter of type ‘int’ which may cause truncation of value [-Werror=absolute-value]
>    545 |  r = abs(right->diff.cycles);
>        |      ^~~
> 
> [jolsa@...va perf]$ gcc --version
> gcc (GCC) 9.1.1 20190503 (Red Hat 9.1.1-1)
> 
> jirka
> 

Thanks for pointing out this issue.

I should use labs()

Thanks
Jin Yao

>>
>> With this patch set, for example,
>>
>>   # perf record -b ./div
>>   # perf record -b ./div
>>   # perf diff -s cycles
>>
>>   # Event 'cycles'
>>   #
>>   # Baseline         Block cycles diff [start:end]  Shared Object     Symbol
>>   # ........  ....................................  ................  ....................................
>>   #
>>       49.03%        -9 [         4ef:         520]  div               [.] main
>>       49.03%         0 [         4e8:         4ea]  div               [.] main
>>       49.03%         0 [         4ef:         500]  div               [.] main
>>       49.03%         0 [         4ef:         51c]  div               [.] main
>>       49.03%         0 [         4ef:         535]  div               [.] main
>>       18.82%         0 [       3ac40:       3ac4d]  libc-2.23.so      [.] __random_r
>>       18.82%         0 [       3ac40:       3ac5c]  libc-2.23.so      [.] __random_r
>>       18.82%         0 [       3ac40:       3ac76]  libc-2.23.so      [.] __random_r
>>       18.82%         0 [       3ac40:       3ac88]  libc-2.23.so      [.] __random_r
>>       18.82%         0 [       3ac90:       3ac9c]  libc-2.23.so      [.] __random_r
>>       16.29%        -8 [       3aac0:       3aac0]  libc-2.23.so      [.] __random
>>       16.29%         0 [       3aac0:       3aad2]  libc-2.23.so      [.] __random
>>       16.29%         0 [       3aae0:       3aae7]  libc-2.23.so      [.] __random
>>       16.29%         0 [       3ab03:       3ab0f]  libc-2.23.so      [.] __random
>>       16.29%         0 [       3ab14:       3ab1b]  libc-2.23.so      [.] __random
>>       16.29%         0 [       3ab28:       3ab2e]  libc-2.23.so      [.] __random
>>       16.29%         0 [       3ab4a:       3ab53]  libc-2.23.so      [.] __random
>>        8.11%         0 [         640:         644]  div               [.] compute_flag
>>        8.11%         0 [         649:         659]  div               [.] compute_flag
>>        5.46%         0 [       3af60:       3af60]  libc-2.23.so      [.] rand
>>        5.46%         0 [       3af60:       3af64]  libc-2.23.so      [.] rand
>>        2.25%         0 [         490:         490]  div               [.] rand@plt
>>        0.01%        26 [      c00a27:      c00a27]  [kernel.vmlinux]  [k] native_irq_return_iret
>>        0.00%      -157 [      2bf9f2:      2bfa63]  [kernel.vmlinux]  [k] update_blocked_averages
>>        0.00%       -56 [      2bf980:      2bf9d3]  [kernel.vmlinux]  [k] update_blocked_averages
>>        0.00%        48 [      2bf934:      2bf942]  [kernel.vmlinux]  [k] update_blocked_averages
>>        0.00%         3 [      2bfb38:      2bfb67]  [kernel.vmlinux]  [k] update_blocked_averages
>>
>> The 'cycles' is a new perf-diff computation selection, which enables
>> the displaying of cycles difference of same program basic block amongst
>> two perf.data. The program basic block is the code block between two
>> branches in a function.
>>
>>   v2:
>>   ---
>>   Keep standard perf diff format.
>>
>>   Following is the v1 output.
>>
>>   # perf diff --basic-block
>>
>>   # Cycles diff  Basic block (start:end)
>>   # ...........  .......................
>>   #
>>            -208  hrtimer_interrupt (30b9e0:30ba42)
>>            -157  update_blocked_averages (2bf9f2:2bfa63)
>>            -126  interrupt_entry (c00880:c0093a)
>>             -86  hrtimer_interrupt (30bb29:30bb32)
>>             -74  hrtimer_interrupt (30ba65:30bac4)
>>             -56  update_blocked_averages (2bf980:2bf9d3)
>>              48  update_blocked_averages (2bf934:2bf942)
>>             -35  native_write_msr (267900:26790b)
>>              26  native_irq_return_iret (c00a27:c00a27)
>>              22  rcu_check_callbacks (2febb6:2febdc)
>>             -21  __hrtimer_run_queues (30b220:30b2a3)
>>              19  pvclock_gtod_notify (14ba0:14c1b)
>>             -18  task_tick_fair (2c5d29:2c5d41)
>>
>> Jin Yao (7):
>>    perf util: Create block_info structure
>>    perf util: Add block_info in hist_entry
>>    perf diff: Check if all data files with branch stacks
>>    perf diff: Use hists to manage basic blocks per symbol
>>    perf diff: Link same basic blocks among different data files
>>    perf diff: Print the basic block cycles diff
>>    perf diff: Documentation -c cycles option
>>
>>   tools/perf/Documentation/perf-diff.txt |  14 +-
>>   tools/perf/builtin-diff.c              | 373 ++++++++++++++++++++++++++++++++-
>>   tools/perf/ui/stdio/hist.c             |  26 +++
>>   tools/perf/util/hist.c                 |  42 +++-
>>   tools/perf/util/hist.h                 |   9 +
>>   tools/perf/util/sort.h                 |   8 +
>>   tools/perf/util/symbol.c               |  22 ++
>>   tools/perf/util/symbol.h               |  23 ++
>>   8 files changed, 509 insertions(+), 8 deletions(-)
>>
>> -- 
>> 2.7.4
>>

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