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Date: Mon, 4 Jun 2007 12:49:07 -0700 (PDT)
From: Jonathan Lim <jlim@....com>
To: jlan@....com (Jay Lan)
Cc: akpm@...ux-foundation.org (Andrew Morton),
muvarov@...mvista.com (Maxim Uvarov),
linux-kernel@...r.kernel.org (LKML),
nagar@...son.ibm.com (Shailabh Nagar),
balbir@...ibm.com (Balbir Singh), daw@....com (David Wright),
jh@....com
Subject: Re: [PATCH] Performance Stats: Kernel patch
Looking at the diffs below, I see context switch counters added. What is
actually being removed?
Jonathan
On Mon Jun 4 12:33:15 2007, jlan@....com wrote:
>
> Add Jonathan Lim to cc, who is working on CSA userland implementation
> to use the taskstats data that this patch is going to remove.
>
> Thanks,
> - jay
>
> Andrew Morton wrote:
> > On Wed, 30 May 2007 18:49:46 +0000
> > Maxim Uvarov <muvarov@...mvista.com> wrote:
> >
> >> Removed syscall counters from patch.
> >>
> >> Patch makes available to the user the following
> >> task and process performance statistics:
> >> * Involuntary Context Switches (task_struct->nivcsw)
> >> * Voluntary Context Switches (task_struct->nvcsw)
> >>
> >> Statistics information is available from:
> >> 1. taskstats interface (Documentation/accounting/)
> >> 2. /proc/PID/status (task only).
> >>
> >> This data is useful for detecting hyperactivity
> >> patterns between processes.
> >> Signed-off-by: Maxim Uvarov <muvarov@...mvista.com>
> >
> > A few little things:
> >
> >> diff --git a/Documentation/accounting/getdelays.c b/Documentation/accounting/getdelays.c
> >> index e9126e7..18d22ad 100644
> >> --- a/Documentation/accounting/getdelays.c
> >> +++ b/Documentation/accounting/getdelays.c
> >> @@ -49,6 +49,7 @@ char name[100];
> >> int dbg;
> >> int print_delays;
> >> int print_io_accounting;
> >> +int print_task_stats;
> >> __u64 stime, utime;
> >>
> >> #define PRINTF(fmt, arg...) { \
> >> @@ -187,7 +188,7 @@ void print_delayacct(struct taskstats *t)
> >> "IO %15s%15s\n"
> >> " %15llu%15llu\n"
> >> "MEM %15s%15s\n"
> >> - " %15llu%15llu\n\n",
> >> + " %15llu%15llu\n"
> >> "count", "real total", "virtual total", "delay total",
> >> t->cpu_count, t->cpu_run_real_total, t->cpu_run_virtual_total,
> >> t->cpu_delay_total,
> >> @@ -196,6 +197,14 @@ void print_delayacct(struct taskstats *t)
> >> "count", "delay total", t->swapin_count, t->swapin_delay_total);
> >> }
> >>
> >> +void print_taskstats(struct taskstats *t)
> >> +{
> >> + printf("\n\nTask %15s%15s\n"
> >> + " %15lu%15lu\n",
> >> + "voluntary", "nonvoluntary",
> >> + t->nvcsw, t->nivcsw);
> >> +}
> >
> > print_task_stats versus print_taskstats is a bit confusing, but I guess it
> > doesn't matter.
> >
> > More significantly, the whole idea of calling it "task stats" isn't a good
> > one: it's far too general. The whole kernel interface is called taskstats,
> > but the additions here are a tiny part of that.
> >
> > Perhaps task_context_switch_rates would be more appropriate, although
> > rather a lot to type.
> >
> >> void print_ioacct(struct taskstats *t)
> >> {
> >> printf("%s: read=%llu, write=%llu, cancelled_write=%llu\n",
> >> @@ -227,7 +236,7 @@ int main(int argc, char *argv[])
> >> struct msgtemplate msg;
> >>
> >> while (1) {
> >> - c = getopt(argc, argv, "diw:r:m:t:p:v:l");
> >> + c = getopt(argc, argv, "qdiw:r:m:t:p:v:l");
> >> if (c < 0)
> >> break;
> >>
> >> @@ -240,6 +249,10 @@ int main(int argc, char *argv[])
> >> printf("printing IO accounting\n");
> >> print_io_accounting = 1;
> >> break;
> >> + case 'q':
> >> + printf("printing task/process stasistics:\n");
> >> + print_task_stats = 1;
> >> + break;
> >> case 'w':
> >> strncpy(logfile, optarg, MAX_FILENAME);
> >> printf("write to file %s\n", logfile);
> >> @@ -381,6 +394,8 @@ int main(int argc, char *argv[])
> >> print_delayacct((struct taskstats *) NLA_DATA(na));
> >> if (print_io_accounting)
> >> print_ioacct((struct taskstats *) NLA_DATA(na));
> >> + if (print_task_stats)
> >> + print_taskstats((struct taskstats *) NLA_DATA(na));
> >> if (fd) {
> >> if (write(fd, NLA_DATA(na), na->nla_len) < 0) {
> >> err(1,"write error\n");
> >> diff --git a/Documentation/accounting/taskstats-struct.txt b/Documentation/accounting/taskstats-struct.txt
> >> index 661c797..c3ae6a9 100644
> >> --- a/Documentation/accounting/taskstats-struct.txt
> >> +++ b/Documentation/accounting/taskstats-struct.txt
> >> @@ -22,6 +22,8 @@ There are three different groups of fields in the struct taskstats:
> >> /* Extended accounting fields end */
> >> Their values are collected if CONFIG_TASK_XACCT is set.
> >>
> >> +4) Per-task and per-thread statistics
> >> +
> >> Future extension should add fields to the end of the taskstats struct, and
> >> should not change the relative position of each field within the struct.
> >>
> >> @@ -158,4 +160,8 @@ struct taskstats {
> >>
> >> /* Extended accounting fields end */
> >>
> >> +4) Per-task and per-thread statistics
> >> + __u64 nvcsw; /* Context voluntary switch counter */
> >> + __u64 nivcsw; /* Context involuntary switch counter */
> >> +
> >> }
> >> diff --git a/fs/proc/array.c b/fs/proc/array.c
> >> index 70e4fab..52e2bd9 100644
> >> --- a/fs/proc/array.c
> >> +++ b/fs/proc/array.c
> >> @@ -290,6 +290,13 @@ static inline char *task_cap(struct task_struct *p, char *buffer)
> >> cap_t(p->cap_permitted),
> >> cap_t(p->cap_effective));
> >> }
> >> +static inline char *task_perf(struct task_struct *p, char *buffer)
> >> +{
> >> + return buffer + sprintf(buffer, "voluntary_ctxt_switches:\t%lu\n"
> >> + "nonvoluntary_ctxt_switches:\t%lu\n",
> >> + p->nvcsw,
> >> + p->nivcsw);
> >> +}
> >
> > And here we call it task_perf, which is inconsistent, and also not very
> > descriptive. Again, task_context_switch_rates would better.
> >
> > err, except it's not a "rate". How about task_context_switches?
> >
> >> int proc_pid_status(struct task_struct *task, char * buffer)
> >> {
> >> @@ -309,6 +316,7 @@ int proc_pid_status(struct task_struct *task, char * buffer)
> >> #if defined(CONFIG_S390)
> >> buffer = task_show_regs(task, buffer);
> >> #endif
> >> + buffer = task_perf(task, buffer);
> >> return buffer - orig;
> >> }
> >>
> >> diff --git a/include/linux/taskstats.h b/include/linux/taskstats.h
> >> index 3fced47..6927f81 100644
> >> --- a/include/linux/taskstats.h
> >> +++ b/include/linux/taskstats.h
> >> @@ -31,7 +31,7 @@
> >> */
> >>
> >>
> >> -#define TASKSTATS_VERSION 3
> >> +#define TASKSTATS_VERSION 4
> >> #define TS_COMM_LEN 32 /* should be >= TASK_COMM_LEN
> >> * in linux/sched.h */
> >>
> >> @@ -146,6 +146,9 @@ struct taskstats {
> >> __u64 read_bytes; /* bytes of read I/O */
> >> __u64 write_bytes; /* bytes of write I/O */
> >> __u64 cancelled_write_bytes; /* bytes of cancelled write I/O */
> >> +
> >> + __u64 nvcsw; /* voluntary_ctxt_switches */
> >> + __u64 nivcsw; /* nonvoluntary_ctxt_switches */
> >> };
> >>
> >>
> >> diff --git a/kernel/taskstats.c b/kernel/taskstats.c
> >> index 4c3476f..e5bc666 100644
> >> --- a/kernel/taskstats.c
> >> +++ b/kernel/taskstats.c
> >> @@ -196,6 +196,8 @@ static int fill_pid(pid_t pid, struct task_struct *tsk,
> >>
> >> /* fill in basic acct fields */
> >> stats->version = TASKSTATS_VERSION;
> >> + stats->nvcsw = tsk->nvcsw;
> >> + stats->nivcsw = tsk->nivcsw;
> >> bacct_add_tsk(stats, tsk);
> >>
> >> /* fill in extended acct fields */
> >> @@ -242,6 +244,8 @@ static int fill_tgid(pid_t tgid, struct task_struct *first,
> >> */
> >> delayacct_add_tsk(stats, tsk);
> >>
> >> + stats->nvcsw += tsk->nvcsw;
> >> + stats->nivcsw += tsk->nivcsw;
> >> } while_each_thread(first, tsk);
> >>
> >> unlock_task_sighand(first, &flags);
> >>
> >
> > The patch otherwise seems OK. Thoughts:
> >
> > - Do we need to increment TASKSTATS_VERSION for this? I forget the rules
> > there.
> >
> > - The lack of context-switch accounting in taskstats is, I think, a
> > simple oversight. It should have been included on day one.
> >
> > There are perhaps other things which _should_ be in taskstats, but we
> > forgot to add them. Can we think of any such things?
> >
> > We shouldn't just toss any old random stuff in there: it should be
> > things which make sense, and which Unix or Linux accounting traditionally
> > provides, and it should be something which we expect won't suddenly
> > become unsupportable if people make internal kernel changes.
-
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