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    SubjectRe: [PATCH 00/28] tracing: 'hist' triggers
    Hi Tom,

    I implemented 'log2' modifier on top of your v11 patchset. Could you
    please take a look at this?



    From 5fc74778b9af5e4e121a0563fb8e54e8f495ca29 Mon Sep 17 00:00:00 2001
    From: Namhyung Kim <namhyung@kernel.org>
    Date: Thu, 5 Nov 2015 23:34:05 +0900
    Subject: [PATCH] tracing: Add hist trigger 'log2' modifier

    Allow users to have numeric fields displayed as log2 values in case
    value range is very wide by appending '.log2' to field names.

    For example,

    # echo 'hist:key=bytes_req' > kmalloc/trigger
    # cat kmalloc/hist

    { bytes_req: 504 } hitcount: 1
    { bytes_req: 11 } hitcount: 1
    { bytes_req: 104 } hitcount: 1
    { bytes_req: 48 } hitcount: 1
    { bytes_req: 2048 } hitcount: 1
    { bytes_req: 4096 } hitcount: 1
    { bytes_req: 240 } hitcount: 1
    { bytes_req: 392 } hitcount: 1
    { bytes_req: 13 } hitcount: 1
    { bytes_req: 28 } hitcount: 1
    { bytes_req: 12 } hitcount: 1
    { bytes_req: 64 } hitcount: 2
    { bytes_req: 128 } hitcount: 2
    { bytes_req: 32 } hitcount: 2
    { bytes_req: 8 } hitcount: 11
    { bytes_req: 10 } hitcount: 13
    { bytes_req: 24 } hitcount: 25
    { bytes_req: 160 } hitcount: 29
    { bytes_req: 16 } hitcount: 33
    { bytes_req: 80 } hitcount: 36

    When using '.log2' modifier, the output looks like:

    # echo 'hist:key=bytes_req.log2' > kmalloc/trigger
    # cat kmalloc/hist

    { bytes_req: ~ 2^12 } hitcount: 1
    { bytes_req: ~ 2^11 } hitcount: 1
    { bytes_req: ~ 2^9 } hitcount: 2
    { bytes_req: ~ 2^6 } hitcount: 3
    { bytes_req: ~ 2^3 } hitcount: 13
    { bytes_req: ~ 2^5 } hitcount: 19
    { bytes_req: ~ 2^8 } hitcount: 49
    { bytes_req: ~ 2^7 } hitcount: 57
    { bytes_req: ~ 2^4 } hitcount: 74

    Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
    Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Signed-off-by: Namhyung Kim <namhyung@kernel.org>
    ---
    kernel/trace/trace.c | 1 +
    kernel/trace/trace_events_hist.c | 18 ++++++++++++++++++
    2 files changed, 19 insertions(+)

    diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
    index 74f95745acbc..542486468707 100644
    --- a/kernel/trace/trace.c
    +++ b/kernel/trace/trace.c
    @@ -3837,6 +3837,7 @@ static const char readme_msg[] =
    "\t .sym-offset display an address as a symbol and offset\n"
    "\t .execname display a common_pid as a program name\n"
    "\t .syscall display a syscall id as a syscall name\n\n"
    + "\t .log2 display log2 value rather than raw number\n\n"
    "\t The 'pause' parameter can be used to pause an existing hist\n"
    "\t trigger or to start a hist trigger but not log any events\n"
    "\t until told to do so. 'continue' can be used to start or\n"
    diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
    index b040ebefcd64..20a17fdb3fe6 100644
    --- a/kernel/trace/trace_events_hist.c
    +++ b/kernel/trace/trace_events_hist.c
    @@ -68,6 +68,13 @@ static u64 hist_field_pstring(struct hist_field *hist_field, void *event)
    return (u64)(unsigned long)*addr;
    }

    +static u64 hist_field_log2(struct hist_field *hist_field, void *event)
    +{
    + u64 val = *(u64 *)(event + hist_field->field->offset);
    +
    + return (u64) ilog2(roundup_pow_of_two(val));
    +}
    +
    #define DEFINE_HIST_FIELD_FN(type) \
    static u64 hist_field_##type(struct hist_field *hist_field, void *event)\
    { \
    @@ -103,6 +110,7 @@ enum hist_field_flags {
    HIST_FIELD_EXECNAME = 64,
    HIST_FIELD_SYSCALL = 128,
    HIST_FIELD_STACKTRACE = 256,
    + HIST_FIELD_LOG2 = 512,
    };

    struct hist_trigger_attrs {
    @@ -349,6 +357,11 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
    goto out;
    }

    + if (flags & HIST_FIELD_LOG2) {
    + hist_field->fn = hist_field_log2;
    + goto out;
    + }
    +
    if (is_string_field(field)) {
    flags |= HIST_FIELD_STRING;

    @@ -500,6 +513,8 @@ static int create_key_field(struct hist_trigger_data *hist_data,
    flags |= HIST_FIELD_EXECNAME;
    else if (!strcmp(field_str, "syscall"))
    flags |= HIST_FIELD_SYSCALL;
    + else if (!strcmp(field_str, "log2"))
    + flags |= HIST_FIELD_LOG2;
    else {
    ret = -EINVAL;
    goto out;
    @@ -942,6 +957,9 @@ hist_trigger_entry_print(struct seq_file *m,
    key + key_field->offset,
    HIST_STACKTRACE_DEPTH);
    multiline = true;
    + } else if (key_field->flags & HIST_FIELD_LOG2) {
    + seq_printf(m, "%s: ~ 2^%-2llu", key_field->field->name,
    + *(u64 *)(key + key_field->offset));
    } else if (key_field->flags & HIST_FIELD_STRING) {
    seq_printf(m, "%s: %-50s", key_field->field->name,
    (char *)(key + key_field->offset));
    --
    2.6.2


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