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Date: Mon, 13 Sep 2021 09:54:00 +0800
From: "Jin, Yao" <yao.jin@...ux.intel.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
Ravi Bangoria <ravi.bangoria@....com>
Cc: mark.rutland@....com, alexander.shishkin@...ux.intel.com,
jolsa@...hat.com, namhyung@...nel.org, kim.phillips@....com,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] perf annotate: Fix fused instr logic for assembly
functions
Hi Arnaldo, Ravi
On 9/12/2021 3:03 AM, Arnaldo Carvalho de Melo wrote:
> Em Sat, Sep 11, 2021 at 10:08:53AM +0530, Ravi Bangoria escreveu:
>> Some x86 microarchitectures fuse a subset of cmp/test/ALU instructions
>> with branch instructions, and thus perf annotate highlight such valid
>> pairs as fused.
>
> Jin, are you ok with this? Can I have your reviewed-by?
>
> - Arnaldo
>
Oh, my original patch could only handle the case like:
cmp xxx
je aaa
But it didn't consider Ravi's case something like:
cmp xxx
cmp yyy
je aaa
je bbb
Thanks for Ravi fixing this issue! Backward searching is probably a better solution.
Frankly I can't reproduce Ravi's case, but for my test suite, Ravi's patch works as well.
Reviewed-by: Jin Yao <yao.jin@...ux.intel.com>
Thanks
Jin Yao
>> When annotated with source, perf uses struct disasm_line to contain
>> either source or instruction line from objdump output. Usually, a C
>> statement generates multiple instructions which include such
>> cmp/test/ALU + branch instruction pairs. But in case of assembly
>> function, each individual assembly source line generate one
>> instruction. Perf annotate instruction fusion logic assumes previous
>> disasm_line as previous instruction line, which is wrong because,
>> for assembly function, previous disasm_line contains source line.
>> And thus perf fails to highlight valid fused instruction pairs for
>> assembly functions.
>>
>> Fix it by searching backward until we find an instruction line and
>> consider that disasm_line as fused with current branch instruction.
>>
>> Before:
>> │ cmpq %rcx, RIP+8(%rsp)
>> 0.00 │ cmp %rcx,0x88(%rsp)
>> │ je .Lerror_bad_iret <--- Source line
>> 0.14 │ ┌──je b4 <--- Instruction line
>> │ │movl %ecx, %eax
>>
>> After:
>> │ cmpq %rcx, RIP+8(%rsp)
>> 0.00 │ ┌──cmp %rcx,0x88(%rsp)
>> │ │je .Lerror_bad_iret
>> 0.14 │ ├──je b4
>> │ │movl %ecx, %eax
>>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
>> ---
>> tools/perf/ui/browser.c | 33 ++++++++++++++++++++++---------
>> tools/perf/ui/browser.h | 2 +-
>> tools/perf/ui/browsers/annotate.c | 24 +++++++++++++++-------
>> 3 files changed, 42 insertions(+), 17 deletions(-)
>>
>> diff --git a/tools/perf/ui/browser.c b/tools/perf/ui/browser.c
>> index 781afe42e90e..fa5bd5c20e96 100644
>> --- a/tools/perf/ui/browser.c
>> +++ b/tools/perf/ui/browser.c
>> @@ -757,25 +757,40 @@ void __ui_browser__line_arrow(struct ui_browser *browser, unsigned int column,
>> }
>>
>> void ui_browser__mark_fused(struct ui_browser *browser, unsigned int column,
>> - unsigned int row, bool arrow_down)
>> + unsigned int row, int diff, bool arrow_down)
>> {
>> - unsigned int end_row;
>> + int end_row;
>>
>> - if (row >= browser->top_idx)
>> - end_row = row - browser->top_idx;
>> - else
>> + if (diff <= 0)
>> return;
>>
>> SLsmg_set_char_set(1);
>>
>> if (arrow_down) {
>> + if (row + diff <= browser->top_idx)
>> + return;
>> +
>> + end_row = row + diff - browser->top_idx;
>> ui_browser__gotorc(browser, end_row, column - 1);
>> - SLsmg_write_char(SLSMG_ULCORN_CHAR);
>> - ui_browser__gotorc(browser, end_row, column);
>> - SLsmg_draw_hline(2);
>> - ui_browser__gotorc(browser, end_row + 1, column - 1);
>> SLsmg_write_char(SLSMG_LTEE_CHAR);
>> +
>> + while (--end_row >= 0 && end_row > (int)(row - browser->top_idx)) {
>> + ui_browser__gotorc(browser, end_row, column - 1);
>> + SLsmg_draw_vline(1);
>> + }
>> +
>> + end_row = (int)(row - browser->top_idx);
>> + if (end_row >= 0) {
>> + ui_browser__gotorc(browser, end_row, column - 1);
>> + SLsmg_write_char(SLSMG_ULCORN_CHAR);
>> + ui_browser__gotorc(browser, end_row, column);
>> + SLsmg_draw_hline(2);
>> + }
>> } else {
>> + if (row < browser->top_idx)
>> + return;
>> +
>> + end_row = row - browser->top_idx;
>> ui_browser__gotorc(browser, end_row, column - 1);
>> SLsmg_write_char(SLSMG_LTEE_CHAR);
>> ui_browser__gotorc(browser, end_row, column);
>> diff --git a/tools/perf/ui/browser.h b/tools/perf/ui/browser.h
>> index 3678eb88f119..510ce4554050 100644
>> --- a/tools/perf/ui/browser.h
>> +++ b/tools/perf/ui/browser.h
>> @@ -51,7 +51,7 @@ void ui_browser__write_graph(struct ui_browser *browser, int graph);
>> void __ui_browser__line_arrow(struct ui_browser *browser, unsigned int column,
>> u64 start, u64 end);
>> void ui_browser__mark_fused(struct ui_browser *browser, unsigned int column,
>> - unsigned int row, bool arrow_down);
>> + unsigned int row, int diff, bool arrow_down);
>> void __ui_browser__show_title(struct ui_browser *browser, const char *title);
>> void ui_browser__show_title(struct ui_browser *browser, const char *title);
>> int ui_browser__show(struct ui_browser *browser, const char *title,
>> diff --git a/tools/perf/ui/browsers/annotate.c b/tools/perf/ui/browsers/annotate.c
>> index ef4da4295bf7..e81c2493efdf 100644
>> --- a/tools/perf/ui/browsers/annotate.c
>> +++ b/tools/perf/ui/browsers/annotate.c
>> @@ -125,13 +125,20 @@ static void annotate_browser__write(struct ui_browser *browser, void *entry, int
>> ab->selection = al;
>> }
>>
>> -static bool is_fused(struct annotate_browser *ab, struct disasm_line *cursor)
>> +static int is_fused(struct annotate_browser *ab, struct disasm_line *cursor)
>> {
>> struct disasm_line *pos = list_prev_entry(cursor, al.node);
>> const char *name;
>> + int diff = 1;
>> +
>> + while (pos && pos->al.offset == -1) {
>> + pos = list_prev_entry(pos, al.node);
>> + if (!ab->opts->hide_src_code)
>> + diff++;
>> + }
>>
>> if (!pos)
>> - return false;
>> + return 0;
>>
>> if (ins__is_lock(&pos->ins))
>> name = pos->ops.locked.ins.name;
>> @@ -139,9 +146,11 @@ static bool is_fused(struct annotate_browser *ab, struct disasm_line *cursor)
>> name = pos->ins.name;
>>
>> if (!name || !cursor->ins.name)
>> - return false;
>> + return 0;
>>
>> - return ins__is_fused(ab->arch, name, cursor->ins.name);
>> + if (ins__is_fused(ab->arch, name, cursor->ins.name))
>> + return diff;
>> + return 0;
>> }
>>
>> static void annotate_browser__draw_current_jump(struct ui_browser *browser)
>> @@ -155,6 +164,7 @@ static void annotate_browser__draw_current_jump(struct ui_browser *browser)
>> struct annotation *notes = symbol__annotation(sym);
>> u8 pcnt_width = annotation__pcnt_width(notes);
>> int width;
>> + int diff = 0;
>>
>> /* PLT symbols contain external offsets */
>> if (strstr(sym->name, "@plt"))
>> @@ -205,11 +215,11 @@ static void annotate_browser__draw_current_jump(struct ui_browser *browser)
>> pcnt_width + 2 + notes->widths.addr + width,
>> from, to);
>>
>> - if (is_fused(ab, cursor)) {
>> + diff = is_fused(ab, cursor);
>> + if (diff > 0) {
>> ui_browser__mark_fused(browser,
>> pcnt_width + 3 + notes->widths.addr + width,
>> - from - 1,
>> - to > from);
>> + from - diff, diff, to > from);
>> }
>> }
>>
>> --
>> 2.27.0
>
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