Messages in this thread | | | Date | Tue, 6 Dec 2011 18:15:21 +0100 | From | Robert Richter <> | Subject | Re: [PATCH 06/10] perf report: Setup browser if stdout is a pipe |
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On 06.12.11 11:29:10, Arnaldo Carvalho de Melo wrote: > commit 46656ac7fb3252f8a3db29b18638e0e8067849ba > Author: Tom Zanussi <tzanussi@gmail.com> > Date: Thu Apr 1 23:59:17 2010 -0500 > > perf report: Introduce special handling for pipe input > > Adds special treatment for stdin - if the user specifies '-i -' > to perf report, the intent is that the event stream be written > to stdin rather than from a disk file. > > The actual handling of the '-' filename is done by the session; > this just adds a signal handler to stop reporting, and turns off > interference by the pager. > > Signed-off-by: Tom Zanussi <tzanussi@gmail.com> > Acked-by: Thomas Gleixner <tglx@linutronix.de> > Cc: fweisbec@gmail.com > Cc: rostedt@goodmis.org > Cc: k-keiichi@bx.jp.nec.com > Cc: acme@ghostprotocols.net > LKML-Reference: <1270184365-8281-4-git-send-email-tzanussi@gmail.com> > Signed-off-by: Ingo Molnar <mingo@elte.hu> > > > I can't understand the comment either, as I think it should've read "the > intent is that the event stream be _read from stdin_ rather than from a > disk file." > > And I don't know what would be the pager interference there. > > Tom, could you elaborate on this?
This patch is part of a patch set introducing "live mode". I guess the intention here is to disable the pager for continuously writing to the terminal and stopping perf with ^C, e.g. (notice the ^C):
# perf record -e <...> -a | perf report # perf record -a -e cpu-cycles | perf report -i - # ======== # captured on: Tue Dec 6 18:09:07 2011 # ======== # ^C# Events: 9 cycles # # Overhead Command Shared Object Symbol [ perf record: Woken up 1 times to write data ] # ........ ....... ................. .............................. # [ perf record: Captured and wrote 0.106 MB (null) (~4627 samples) ] [...]
A pager would catch the ^C, also an appended pipe. So, my version also does not work for this case, suggest to skip this patch first in favor of a better solution.
But will have to rework the next patch because a potential null pointer access to input_name.
-Robert
-- Advanced Micro Devices, Inc. Operating System Research Center
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