lkml.org 
[lkml]   [2018]   [Mar]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [RFC 0/4] trace_uprobe: Support SDT markers having semaphore
    From
    Date


    On 02/28/2018 07:55 PM, Masami Hiramatsu wrote:
    > Hi Ravi,
    >
    > Thank you for your great work!

    Thanks Masami.

    > On Wed, 28 Feb 2018 13:23:41 +0530
    > Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> wrote:
    >
    >> Userspace Statically Defined Tracepoints[1] are dtrace style markers
    >> inside userspace applications. These markers are added by developer at
    >> important places in the code. Each marker source expands to a single
    >> nop instruction in the compiled code but there may be additional
    >> overhead for computing the marker arguments which expands to couple of
    >> instructions. If this computaion is quite more, execution of it can be
    >> ommited by runtime if() condition when no one is tracing on the marker:
    ...
    >>
    >> Semaphore offset is 0x10036. I don't have educated 'perf probe'
    >> about semaphore. So instead of using 'perf probe' command, I'm
    >> manually adding entry in the <tracefs>/uprobe_events file.
    > Ok, it is easy to pass semaphore address via perf probe :)

    Yes, it should be fairly easy to parse semaphore at buildid-cache time.
    Will add a patch for that.

    >
    >> Special char * denotes semaphore offset.
    >>
    >>
    >> # echo "p:sdt_tick/loop2 /tmp/tick:0x6e4 *0x10036" > uprobe_events
    > IMHO, this syntax is no good, separate with space is only for arguments.
    > Since the semaphore is per-probe-point based, that should be specified with probe point.
    > (there are no 2 or more semaphores on 1 event, are there?)
    > So something like
    >
    > # echo "p:sdt_tick/loop2 /tmp/tick:0x6e4(0x10036)" > uprobe_events

    This is great suggestion. Will change it.

    Please review patch 3 and 4 which contains actual implementation.

    Thanks for the review,
    Ravi

    \
     
     \ /
      Last update: 2018-03-01 06:31    [W:3.742 / U:0.172 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site