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  1. 12 Nov, 2009 1 commit
    • Steven Rostedt's avatar
      ring-buffer: Add multiple iterations between benchmark timestamps · a6f0eb6a
      Steven Rostedt authored 
      The ring_buffer_benchmark does a gettimeofday after every write to the
ring buffer in its measurements. This adds the overhead of the call
to gettimeofday to the measurements and does not give an accurate picture
of the length of time it takes to record a trace.

This was first noticed with perf top:

------------------------------------------------------------------------------
   PerfTop:     679 irqs/sec  kernel:99.9% [1000Hz cpu-clock-msecs],  (all, 4 CPUs)
------------------------------------------------------------------------------

             samples    pcnt   kernel function
             _______   _____   _______________

             1673.00 - 27.8% : trace_clock_local
              806.00 - 13.4% : do_gettimeofday
              590.00 -  9.8% : rb_reserve_next_event
              554.00 -  9.2% : native_read_tsc
              431.00 -  7.2% : ring_buffer_lock_reserve
              365.00 -  6.1% : __rb_reserve_next
              355.00 -  5.9% : rb_end_commit
              322.00 -  5.4% : getnstimeofday
              268.00 -  4.5% : ring_buffer_unlock_commit
              262.00 -  4.4% : ring_buffer_producer_thread 	[ring_buffer_benchmark]
              113.00 -  1.9% : read_tsc
               91.00 -  1.5% : debug_smp_processor_id
               69.00 -  1.1% : trace_recursive_unlock
               66.00 -  1.1% : ring_buffer_event_data
               25.00 -  0.4% : _spin_unlock_irq

And the length of each write to the ring buffer measured at 310ns.

This patch adds a new module parameter called "write_interval" which is
defaulted to 50. This is the number of writes performed between
timestamps. After this patch perf top shows:

------------------------------------------------------------------------------
   PerfTop:     244 irqs/sec  kernel:100.0% [1000Hz cpu-clock-msecs],  (all, 4 CPUs)
------------------------------------------------------------------------------

             samples    pcnt   kernel function
             _______   _____   _______________

             2842.00 - 40.4% : trace_clock_local
             1043.00 - 14.8% : rb_reserve_next_event
              784.00 - 11.1% : ring_buffer_lock_reserve
              600.00 -  8.5% : __rb_reserve_next
              579.00 -  8.2% : rb_end_commit
              440.00 -  6.3% : ring_buffer_unlock_commit
              290.00 -  4.1% : ring_buffer_producer_thread 	[ring_buffer_benchmark]
              155.00 -  2.2% : debug_smp_processor_id
              117.00 -  1.7% : trace_recursive_unlock
              103.00 -  1.5% : ring_buffer_event_data
               28.00 -  0.4% : do_gettimeofday
               22.00 -  0.3% : _spin_unlock_irq
               14.00 -  0.2% : native_read_tsc
               11.00 -  0.2% : getnstimeofday

do_gettimeofday dropped from 13% usage to a mere 0.4%! (using the default
50 interval)  The measurement for each timestamp went from 310ns to 210ns.
That's 100ns (1/3rd) overhead that the gettimeofday call was introducing.
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      a6f0eb6a
  3. 02 Nov, 2009 3 commits
  5. 29 Oct, 2009 9 commits
  7. 24 Oct, 2009 4 commits
  9. 22 Oct, 2009 8 commits
  11. 21 Oct, 2009 14 commits
  13. 20 Oct, 2009 1 commit
    • Andreas Gruenbacher's avatar
      dnotify: ignore FS_EVENT_ON_CHILD · 94552684
      Andreas Gruenbacher authored 
      Mask off FS_EVENT_ON_CHILD in dnotify_handle_event().  Otherwise, when there
is more than one watch on a directory and dnotify_should_send_event()
succeeds, events with FS_EVENT_ON_CHILD set will trigger all watches and cause
spurious events.

This case was overlooked in commit e42e2773.

	#define _GNU_SOURCE

	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <signal.h>
	#include <sys/types.h>
	#include <sys/stat.h>
	#include <fcntl.h>
	#include <string.h>

	static void create_event(int s, siginfo_t* si, void* p)
	{
		printf("create\n");
	}

	static void delete_event(int s, siginfo_t* si, void* p)
	{
		printf("delete\n");
	}

	int main (void) {
		struct sigaction action;
		char *tmpdir, *file;
		int fd1, fd2;

		sigemptyset (&action.sa_mask);
		action.sa_flags = SA_SIGINFO;

		action.sa_sigaction = create_event;
		sigaction (SIGRTMIN + 0, &action, NULL);

		action.sa_sigaction = delete_event;
		sigaction (SIGRTMIN + 1, &action, NULL);

	#	define TMPDIR "/tmp/test.XXXXXX"
		tmpdir = malloc(strlen(TMPDIR) + 1);
		strcpy(tmpdir, TMPDIR);
		mkdtemp(tmpdir);

	#	define TMPFILE "/file"
		file = malloc(strlen(tmpdir) + strlen(TMPFILE) + 1);
		sprintf(file, "%s/%s", tmpdir, TMPFILE);

		fd1 = open (tmpdir, O_RDONLY);
		fcntl(fd1, F_SETSIG, SIGRTMIN);
		fcntl(fd1, F_NOTIFY, DN_MULTISHOT | DN_CREATE);

		fd2 = open (tmpdir, O_RDONLY);
		fcntl(fd2, F_SETSIG, SIGRTMIN + 1);
		fcntl(fd2, F_NOTIFY, DN_MULTISHOT | DN_DELETE);

		if (fork()) {
			/* This triggers a create event */
			creat(file, 0600);
			/* This triggers a create and delete event (!) */
			unlink(file);
		} else {
			sleep(1);
			rmdir(tmpdir);
		}

		return 0;
	}
Signed-off-by: default avatarAndreas Gruenbacher <agruen@suse.de>
Signed-off-by: default avatarEric Paris <eparis@redhat.com>
      94552684