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perf_counter: Sleep before refresh using poll in perf top 

perf top is refreshed every delay_secs the thread runs in such
loop:

while (sleep(delay_secs)) {
	print_sym_table();
}

At the end of print_sym_table(), poll is used without sleep delay
to check if we have something from stdin.

It means that this check is done only every delay_secs, which can
be higher that 2 secs if the user defined a custom refresh rate.

We can drop sleep() here and directly use poll to wait between
refresh periods, so that the reaction after the user stops perf top
after typing "Enter" is immediate and doesn't suffer from the
delay_secs latency.

Nb: poll doesn't add any overhead that can parasite perf top measures
since it sleeps the entire timeout here.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1244141284-7507-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
hifive-unleashed-5.1
Frederic Weisbecker 2009-06-04 20:48:04 +02:00 committed by Ingo Molnar
parent 62fc44536c
commit 0f5486b5c7
1 changed files with 9 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
Documentation/perf_counter/builtin-top.c
View File

@ -204,7 +204,7 @@ static void print_sym_table(void)
list_remove_active_sym(syme);
}
write(1, CONSOLE_CLEAR, strlen(CONSOLE_CLEAR));
puts(CONSOLE_CLEAR);
printf(
"------------------------------------------------------------------------------\n");
@ -278,23 +278,21 @@ static void print_sym_table(void)
color_fprintf(stdout, color, "%4.1f%%", pcnt);
printf(" - %016llx : %s\n", sym->start, sym->name);
}
{
struct pollfd stdin_poll = { .fd = 0, .events = POLLIN };
if (poll(&stdin_poll, 1, 0) == 1) {
printf("key pressed - exiting.\n");
exit(0);
}
}
}
static void *display_thread(void *arg)
{
struct pollfd stdin_poll = { .fd = 0, .events = POLLIN };
int delay_msecs = delay_secs * 1000;
printf("PerfTop refresh period: %d seconds\n", delay_secs);
while (!sleep(delay_secs))
do {
print_sym_table();
} while (!poll(&stdin_poll, 1, delay_msecs) == 1);
printf("key pressed - exiting.\n");
exit(0);
return NULL;
}