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Message-ID: <4664725D.6080908@sgi.com>
Date: Mon, 04 Jun 2007 13:13:17 -0700
From: Jay Lan <jlan@....com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: Maxim Uvarov <muvarov@...mvista.com>,
LKML <linux-kernel@...r.kernel.org>,
Shailabh Nagar <nagar@....com>,
Balbir Singh <balbir@...ibm.com>,
Jay Lan <jlan@...ulhu.engr.sgi.com>
Subject: Re: [PATCH] Performance Stats: Kernel patch
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.
As long as we change the size of taskstats struct or the relative
position of existing fields, or the taskstats interface, we need to
increment the TASKSTATS_VERSION. I guess if we make more than one
changes within one 2.6.x release cycle, we can bundle them in one
version change. Shailabh or Balbir?
Thanks,
- jay
>
> - 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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