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    SubjectRe: [PATCH v2 0/7] perf diff: diff cycles at basic block level
    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@krava perf]$ gcc --version
    gcc (GCC) 9.1.1 20190503 (Red Hat 9.1.1-1)

    jirka

    >
    > 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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