Re: [Qemu-devel] [PATCH 2/5] trace-cmd: Use tracing directory to count CPUs
On Thu, 2012-08-23 at 12:00 +0900, Masami Hiramatsu wrote: (2012/08/23 11:01), Masami Hiramatsu wrote: (2012/08/22 22:41), Steven Rostedt wrote: On Wed, 2012-08-22 at 17:43 +0900, Yoshihiro YUNOMAE wrote: From: Masami Hiramatsu masami.hiramatsu...@hitachi.com Count debugfs/tracing/per_cpu/cpu* to determine the number of CPUs. I'm curious, do you find that sysconf doesn't return the # of CPUs the system has? No, sysconf returns the number of hosts CPUs, not guests. I've had boxes where the per_cpu/cpu* had more cpus than the box actually holds. But this was a bug in the kernel, not the tool. This change log needs to have rational instead of just explaining what the patch does. Ah, I see. Hmm, then this should be enabled by a command line option or an environment variable. Oops, I misunderstood. I'll add more comment for why this should be tried instead of sysconf. And now that I understand why you are doing this, why not only do this if the TRACE_AGENT or DEBUG_TRACING_DIR is defined. That is, if we are doing it against a bare metal system, then sysconf should suffice, but if we are tracing against a guest, then it should use the tracing directory to determine the buffers. We could add options to override this, but I would think the default should just Do The Right Thing(tm). -- Steve
Re: [Qemu-devel] [PATCH 2/5] trace-cmd: Use tracing directory to count CPUs
(2012/08/23 18:08), Steven Rostedt wrote: On Thu, 2012-08-23 at 12:00 +0900, Masami Hiramatsu wrote: (2012/08/23 11:01), Masami Hiramatsu wrote: (2012/08/22 22:41), Steven Rostedt wrote: On Wed, 2012-08-22 at 17:43 +0900, Yoshihiro YUNOMAE wrote: From: Masami Hiramatsu masami.hiramatsu...@hitachi.com Count debugfs/tracing/per_cpu/cpu* to determine the number of CPUs. I'm curious, do you find that sysconf doesn't return the # of CPUs the system has? No, sysconf returns the number of hosts CPUs, not guests. I've had boxes where the per_cpu/cpu* had more cpus than the box actually holds. But this was a bug in the kernel, not the tool. This change log needs to have rational instead of just explaining what the patch does. Ah, I see. Hmm, then this should be enabled by a command line option or an environment variable. Oops, I misunderstood. I'll add more comment for why this should be tried instead of sysconf. And now that I understand why you are doing this, why not only do this if the TRACE_AGENT or DEBUG_TRACING_DIR is defined. That is, if we are doing it against a bare metal system, then sysconf should suffice, but if we are tracing against a guest, then it should use the tracing directory to determine the buffers. We could add options to override this, but I would think the default should just Do The Right Thing(tm). Yeah, so I'd like to push this is the default method, and fix the kernel bug (but I'm not sure that is a bug). Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com
[Qemu-devel] [PATCH 2/5] trace-cmd: Use tracing directory to count CPUs
From: Masami Hiramatsu masami.hiramatsu...@hitachi.com
Count debugfs/tracing/per_cpu/cpu* to determine the
number of CPUs.
Signed-off-by: Masami Hiramatsu masami.hiramatsu...@hitachi.com
Signed-off-by: Yoshihiro YUNOMAE yoshihiro.yunomae...@hitachi.com
---
trace-record.c | 41 +
1 files changed, 41 insertions(+), 0 deletions(-)
diff --git a/trace-record.c b/trace-record.c
index 9dc18a9..ed18951 100644
--- a/trace-record.c
+++ b/trace-record.c
@@ -1179,6 +1179,41 @@ static void expand_event_list(void)
}
}
+static int count_tracingdir_cpus(void)
+{
+ char *tracing_dir = NULL;
+ char *percpu_dir = NULL;
+ struct dirent **namelist;
+ int count = 0, n;
+
+ /* Count cpus in per_cpu directory */
+ tracing_dir = tracecmd_find_tracing_dir();
+ if (!tracing_dir)
+ return 0;
+ percpu_dir = malloc_or_die(strlen(tracing_dir) + 9);
+ if (!percpu_dir)
+ goto err;
+
+ sprintf(percpu_dir, %s/per_cpu, tracing_dir);
+
+ n = scandir(percpu_dir, namelist, NULL, alphasort);
+ if (n 0) {
+ while (n--) {
+ if (strncmp(cpu, namelist[n]-d_name, 3) == 0)
+ count++;
+ free(namelist[n]);
+ }
+ free(namelist);
+ }
+
+ if (percpu_dir)
+ free(percpu_dir);
+err:
+ if (tracing_dir)
+ free(tracing_dir);
+ return count;
+}
+
static int count_cpus(void)
{
FILE *fp;
@@ -1189,6 +1224,12 @@ static int count_cpus(void)
size_t n;
int r;
+ cpus = count_tracingdir_cpus();
+ if (cpus 0)
+ return cpus;
+
+ warning(failed to use tracing_dir to determine number of CPUS);
+
cpus = sysconf(_SC_NPROCESSORS_CONF);
if (cpus 0)
return cpus;
Re: [Qemu-devel] [PATCH 2/5] trace-cmd: Use tracing directory to count CPUs
On Wed, 2012-08-22 at 17:43 +0900, Yoshihiro YUNOMAE wrote: From: Masami Hiramatsu masami.hiramatsu...@hitachi.com Count debugfs/tracing/per_cpu/cpu* to determine the number of CPUs. I'm curious, do you find that sysconf doesn't return the # of CPUs the system has? I've had boxes where the per_cpu/cpu* had more cpus than the box actually holds. But this was a bug in the kernel, not the tool. This change log needs to have rational instead of just explaining what the patch does. Thanks, -- Steve Signed-off-by: Masami Hiramatsu masami.hiramatsu...@hitachi.com Signed-off-by: Yoshihiro YUNOMAE yoshihiro.yunomae...@hitachi.com ---
Re: [Qemu-devel] [PATCH 2/5] trace-cmd: Use tracing directory to count CPUs
(2012/08/22 22:41), Steven Rostedt wrote: On Wed, 2012-08-22 at 17:43 +0900, Yoshihiro YUNOMAE wrote: From: Masami Hiramatsu masami.hiramatsu...@hitachi.com Count debugfs/tracing/per_cpu/cpu* to determine the number of CPUs. I'm curious, do you find that sysconf doesn't return the # of CPUs the system has? No, sysconf returns the number of hosts CPUs, not guests. I've had boxes where the per_cpu/cpu* had more cpus than the box actually holds. But this was a bug in the kernel, not the tool. This change log needs to have rational instead of just explaining what the patch does. Ah, I see. Hmm, then this should be enabled by a command line option or an environment variable. Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com
Re: [Qemu-devel] [PATCH 2/5] trace-cmd: Use tracing directory to count CPUs
(2012/08/23 11:01), Masami Hiramatsu wrote: (2012/08/22 22:41), Steven Rostedt wrote: On Wed, 2012-08-22 at 17:43 +0900, Yoshihiro YUNOMAE wrote: From: Masami Hiramatsu masami.hiramatsu...@hitachi.com Count debugfs/tracing/per_cpu/cpu* to determine the number of CPUs. I'm curious, do you find that sysconf doesn't return the # of CPUs the system has? No, sysconf returns the number of hosts CPUs, not guests. I've had boxes where the per_cpu/cpu* had more cpus than the box actually holds. But this was a bug in the kernel, not the tool. This change log needs to have rational instead of just explaining what the patch does. Ah, I see. Hmm, then this should be enabled by a command line option or an environment variable. Oops, I misunderstood. I'll add more comment for why this should be tried instead of sysconf. Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com
