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Message-ID: <46F559A5.5060900@linux.vnet.ibm.com>
Date: Sat, 22 Sep 2007 23:36:29 +0530
From: Balbir Singh <balbir@...ux.vnet.ibm.com>
To: Guillaume Chazarain <guichaz@...oo.fr>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Oleg Nesterov <oleg@...sign.ru>, Jonathan Lim <jlim@....com>,
Jay Lan <jlan@...ulhu.engr.sgi.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] taskstats: separate PID/TGID stats producers to complete
the TGID ones
Guillaume Chazarain wrote:
> TASKSTATS_CMD_ATTR_TGID used to return only the delay accounting stats, not
> the basic and extended accounting. With this patch,
> TASKSTATS_CMD_ATTR_TGID also aggregates the accounting info for all threads
> of a thread group.
>
> TASKSTATS_CMD_ATTR_PID output should be unchanged
> TASKSTATS_CMD_ATTR_TGID output should have all fields set, unlike before the
> patch where most of the fiels were set to 0.
>
> To this aim, two functions were introduced: fill_threadgroup() and add_tsk().
> These functions are responsible for aggregating the subsystem specific
> accounting information. Taskstats requesters (fill_pid(), fill_tgid() and
> fill_tgid_exit()) should only call add_tsk() and fill_threadgroup() to get the
> stats.
>
> Signed-off-by: Guillaume Chazarain <guichaz@...oo.fr>
> Cc: Balbir Singh <balbir@...ibm.com>
> Cc: Jay Lan <jlan@...r.sgi.com>
> Cc: Jonathan Lim <jlim@....com>
> Cc: Oleg Nesterov <oleg@...sign.ru>
> ---
>
> Documentation/accounting/getdelays.c | 2 -
> include/linux/tsacct_kern.h | 12 ++-
> kernel/taskstats.c | 131 ++++++++++++++++++++++------------
> kernel/tsacct.c | 106 ++++++++++++++++------------
> 4 files changed, 155 insertions(+), 96 deletions(-)
>
> diff --git a/Documentation/accounting/getdelays.c b/Documentation/accounting/getdelays.c
> index cbee3a2..78773c0 100644
> --- a/Documentation/accounting/getdelays.c
> +++ b/Documentation/accounting/getdelays.c
> @@ -76,7 +76,7 @@ static void usage(void)
> fprintf(stderr, "getdelays [-dilv] [-w logfile] [-r bufsize] "
> "[-m cpumask] [-t tgid] [-p pid]\n");
> fprintf(stderr, " -d: print delayacct stats\n");
> - fprintf(stderr, " -i: print IO accounting (works only with -p)\n");
> + fprintf(stderr, " -i: print IO accounting\n");
> fprintf(stderr, " -l: listen forever\n");
> fprintf(stderr, " -v: debug on\n");
> }
> diff --git a/include/linux/tsacct_kern.h b/include/linux/tsacct_kern.h
> index 7e50ac7..93dffc2 100644
> --- a/include/linux/tsacct_kern.h
> +++ b/include/linux/tsacct_kern.h
> @@ -10,17 +10,23 @@
> #include <linux/taskstats.h>
>
> #ifdef CONFIG_TASKSTATS
> -extern void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk);
> +void bacct_fill_threadgroup(struct taskstats *stats, struct task_struct *task);
> +void bacct_add_tsk(struct taskstats *stats, struct task_struct *task);
> #else
> -static inline void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
> +static inline void bacct_fill_threadgroup(struct taskstats *stats, struct task_struct *task)
> +{}
> +static inline void bacct_add_tsk(struct taskstats *stats, struct task_struct *task)
> {}
> #endif /* CONFIG_TASKSTATS */
>
> #ifdef CONFIG_TASK_XACCT
> -extern void xacct_add_tsk(struct taskstats *stats, struct task_struct *p);
> +void xacct_fill_threadgroup(struct taskstats *stats, struct task_struct *task);
> +void xacct_add_tsk(struct taskstats *stats, struct task_struct *p);
> extern void acct_update_integrals(struct task_struct *tsk);
> extern void acct_clear_integrals(struct task_struct *tsk);
> #else
> +static inline void xacct_fill_threadgroup(struct taskstats *stats, struct task_struct *task)
> +{}
> static inline void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
> {}
> static inline void acct_update_integrals(struct task_struct *tsk)
> diff --git a/kernel/taskstats.c b/kernel/taskstats.c
> index 059431e..ce43fae 100644
> --- a/kernel/taskstats.c
> +++ b/kernel/taskstats.c
> @@ -168,6 +168,68 @@ static void send_cpu_listeners(struct sk_buff *skb,
> up_write(&listeners->sem);
> }
>
> +/**
> + * fill_threadgroup - initialize some common stats for the thread group
> + * @stats: the taskstats to write into
> + * @task: the thread representing the whole group
> + *
> + * There are two types of taskstats fields when considering a thread group:
> + * - those that can be aggregated from each thread in the group (like CPU
> + * times),
> + * - those that cannot be aggregated (like UID) or are identical (like
> + * memory usage), so are taken from the group leader.
> + * XXX_threadgroup() methods deal with the first type while XXX_add_tsk() with
> + * the second.
> + */
> +static void fill_threadgroup(struct taskstats *stats, struct task_struct *task)
> +{
How about calling this one fill_threadgroup_stats()?
> + /*
> + * Each accounting subsystem adds calls to its functions to initialize
> + * relevant parts of struct taskstsats for a single tgid as follows:
> + *
> + * per-task-foo-fill_threadgroup(stats, task);
> + */
> +
> + stats->version = TASKSTATS_VERSION;
> +
> + /* fill in basic acct fields */
> + bacct_fill_threadgroup(stats, task);
> +
> + /* fill in extended acct fields */
> + xacct_fill_threadgroup(stats, task);
> +}
> +
> +/**
> + * add_tsk - combine some thread specific stats in a taskstats
> + * @stats: the taskstats to write into
> + * @task: the thread to combine
> + *
> + * Stats specific to each thread in the thread group. Stats of @task should be
> + * combined with those already present in @stats. add_tsk() works in
> + * conjunction with fill_threadgroup(), taskstats fields should not be touched
> + * by both functions.
> + */
> +static void add_tsk(struct taskstats *stats, struct task_struct *task)
> +{
How about we call function add_tsk_stats()?
> + /*
> + * Each accounting subsystem adds calls to its functions to combine
> + * relevant parts of struct taskstsats for a single pid as follows:
> + *
> + * per-task-foo-add_tsk(stats, task);
> + */
> + stats->nvcsw += task->nvcsw;
> + stats->nivcsw += task->nivcsw;
> +
> + /* fill in delay acct fields */
> + delayacct_add_tsk(stats, task);
> +
> + /* fill in basic acct fields */
> + bacct_add_tsk(stats, task);
> +
> + /* fill in extended acct fields */
> + xacct_add_tsk(stats, task);
> +}
> +
> static int fill_pid(pid_t pid, struct task_struct *tsk,
> struct taskstats *stats)
> {
> @@ -185,23 +247,8 @@ static int fill_pid(pid_t pid, struct task_struct *tsk,
> get_task_struct(tsk);
>
> memset(stats, 0, sizeof(*stats));
> - /*
> - * Each accounting subsystem adds calls to its functions to
> - * fill in relevant parts of struct taskstsats as follows
> - *
> - * per-task-foo(stats, tsk);
> - */
> -
> - delayacct_add_tsk(stats, 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 */
> - xacct_add_tsk(stats, tsk);
> + add_tsk(stats, tsk);
> + fill_threadgroup(stats, tsk);
>
So we always call fill_threadgroup later, is there a reason for
that. Can the order of calls be arbitrary or is there a dependency?
> /* Define err: label here if needed */
> put_task_struct(tsk);
> @@ -233,31 +280,20 @@ static int fill_tgid(pid_t tgid, struct task_struct *first,
> memset(stats, 0, sizeof(*stats));
>
> tsk = first;
> - do {
> - if (tsk->exit_state)
> - continue;
> - /*
> - * Accounting subsystem can call its functions here to
> - * fill in relevant parts of struct taskstsats as follows
> - *
> - * per-task-foo(stats, tsk);
> - */
> - delayacct_add_tsk(stats, tsk);
> -
> - stats->nvcsw += tsk->nvcsw;
> - stats->nivcsw += tsk->nivcsw;
> - } while_each_thread(first, tsk);
> -
> + do
> + if (!tsk->exit_state)
> + /*
> + * This check is racy as a thread could exit just right
> + * now and have its statistics accounted twice.
> + */
> + add_tsk(stats, tsk);
> + while_each_thread(first, tsk);
> +
I still prefer braces around do <--> while, I think the code is easier
to read with them.
> + fill_threadgroup(stats, first->group_leader);
> unlock_task_sighand(first, &flags);
> rc = 0;
> out:
> rcu_read_unlock();
> -
> - stats->version = TASKSTATS_VERSION;
> - /*
> - * Accounting subsytems can also add calls here to modify
> - * fields of taskstats.
> - */
> return rc;
> }
>
> @@ -267,19 +303,14 @@ static void fill_tgid_exit(struct task_struct *tsk)
> unsigned long flags;
>
> spin_lock_irqsave(&tsk->sighand->siglock, flags);
> - if (!tsk->signal->stats)
> - goto ret;
>
> /*
> - * Each accounting subsystem calls its functions here to
> - * accumalate its per-task stats for tsk, into the per-tgid structure
> - *
> - * per-task-foo(tsk->signal->stats, tsk);
> + * The fill_threadgroup() part of the statistics will be added by the
> + * stats requester, i.e. fill_tgid() or taskstats_exit()
> */
> - delayacct_add_tsk(tsk->signal->stats, tsk);
> -ret:
> + add_tsk(tsk->signal->stats, tsk);
> +
> spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
> - return;
> }
>
> static int add_del_listener(pid_t pid, cpumask_t *maskp, int isadd)
> @@ -508,7 +539,13 @@ void taskstats_exit(struct task_struct *tsk, int group_dead)
> if (!stats)
> goto err;
>
> + /*
> + * Race here: the last thread may have not finished its
> + * fill_tgid_exit(), leaving an incomplete tsk->signal->stats
> + */
> +
> memcpy(stats, tsk->signal->stats, sizeof(*stats));
> + fill_threadgroup(stats, tsk->group_leader);
>
> send:
> send_cpu_listeners(rep_skb, listeners);
> diff --git a/kernel/tsacct.c b/kernel/tsacct.c
> index 4ab1b58..9541a1a 100644
> --- a/kernel/tsacct.c
> +++ b/kernel/tsacct.c
> @@ -22,54 +22,68 @@
> #include <linux/acct.h>
> #include <linux/jiffies.h>
>
> -/*
> - * fill in basic accounting fields
> - */
Could we further split the tsacct and delayacct/taskstats patches.
> -void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
> +static void fill_wall_times(struct taskstats *stats, struct task_struct *tsk)
> {
> struct timespec uptime, ts;
> s64 ac_etime;
>
> - BUILD_BUG_ON(TS_COMM_LEN < TASK_COMM_LEN);
> -
> /* calculate task elapsed time in timespec */
> do_posix_clock_monotonic_gettime(&uptime);
> ts = timespec_sub(uptime, tsk->start_time);
> /* rebase elapsed time to usec */
> ac_etime = timespec_to_ns(&ts);
> do_div(ac_etime, NSEC_PER_USEC);
> - stats->ac_etime = ac_etime;
> - stats->ac_btime = get_seconds() - ts.tv_sec;
> - if (thread_group_leader(tsk)) {
> - stats->ac_exitcode = tsk->exit_code;
> - if (tsk->flags & PF_FORKNOEXEC)
> + stats->ac_etime = ac_etime;
> + stats->ac_btime = get_seconds() - ts.tv_sec;
> +}
> +
> +/*
> + * fill in basic accounting fields
> + */
> +
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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