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    Subject[Patch 6/8] delay accounting usage of taskstats interface
    Changelog

    Fixes comments by akpm (on earlier patch now incorporated here)
    - detailed comments on atomicity rules of accounting fields
    - replace use of nsec_t


    delayacct-taskstats.patch

    Usage of taskstats interface by delay accounting.


    Signed-off-by: Shailabh Nagar <nagar@us.ibm.com>
    Signed-off-by: Balbir Singh <balbir@in.ibm.com>


    include/linux/delayacct.h | 11 ++++++++++
    include/linux/taskstats.h | 48 +++++++++++++++++++++++++++++++++++++++++++++-
    init/Kconfig | 1
    kernel/delayacct.c | 42 ++++++++++++++++++++++++++++++++++++++++
    kernel/taskstats.c | 9 +++++++-
    5 files changed, 109 insertions(+), 2 deletions(-)

    Index: linux-2.6.17-rc1/include/linux/delayacct.h
    ===================================================================
    --- linux-2.6.17-rc1.orig/include/linux/delayacct.h 2006-04-21 20:29:13.000000000 -0400
    +++ linux-2.6.17-rc1/include/linux/delayacct.h 2006-04-21 20:42:41.000000000 -0400
    @@ -18,6 +18,7 @@
    #define _LINUX_TASKDELAYS_H

    #include <linux/sched.h>
    +#include <linux/taskstats_kern.h>

    /*
    * Per-task flags relevant to delay accounting
    @@ -35,6 +36,7 @@ extern void __delayacct_tsk_init(struct
    extern void __delayacct_tsk_exit(struct task_struct *);
    extern void __delayacct_blkio_start(void);
    extern void __delayacct_blkio_end(void);
    +extern int __delayacct_add_tsk(struct taskstats *, struct task_struct *);

    static inline void delayacct_set_flag(int flag)
    {
    @@ -74,6 +76,13 @@ static inline void delayacct_blkio_end(v
    __delayacct_blkio_end();
    }

    +static inline int delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
    +{
    + if (!tsk->delays)
    + return -EINVAL;
    + return __delayacct_add_tsk(d, tsk);
    +}
    +
    #else
    static inline void delayacct_set_flag(int flag)
    {}
    @@ -89,6 +98,8 @@ static inline void delayacct_blkio_start
    {}
    static inline void delayacct_blkio_end(void)
    {}
    +static inline int delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
    +{ return 0; }
    #endif /* CONFIG_TASK_DELAY_ACCT */

    #endif
    Index: linux-2.6.17-rc1/kernel/delayacct.c
    ===================================================================
    --- linux-2.6.17-rc1.orig/kernel/delayacct.c 2006-04-21 20:29:13.000000000 -0400
    +++ linux-2.6.17-rc1/kernel/delayacct.c 2006-04-21 20:40:03.000000000 -0400
    @@ -104,3 +104,45 @@ void __delayacct_blkio_end(void)
    &current->delays->blkio_delay,
    &current->delays->blkio_count);
    }
    +
    +int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
    +{
    + s64 tmp;
    + struct timespec ts;
    + unsigned long t1,t2,t3;
    +
    +
    + tmp = (s64)d->cpu_run_real_total;
    + tmp += (u64)(tsk->utime + tsk->stime) * TICK_NSEC;
    + d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
    +
    + /* No locking available for sched_info (and too expensive to add one)
    + * Mitigate by taking snapshot of values
    + */
    + t1 = tsk->sched_info.pcnt;
    + t2 = tsk->sched_info.run_delay;
    + t3 = tsk->sched_info.cpu_time;
    +
    + d->cpu_count += t1;
    +
    + jiffies_to_timespec(t2, &ts);
    + tmp = (s64)d->cpu_delay_total + timespec_to_ns(&ts);
    + d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
    +
    + tmp = (s64)d->cpu_run_virtual_total + (s64)jiffies_to_usecs(t3) * 1000;
    + d->cpu_run_virtual_total =
    + (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
    +
    + /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
    +
    + spin_lock(&tsk->delays->lock);
    + tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
    + d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
    + tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
    + d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
    + d->blkio_count += tsk->delays->blkio_count;
    + d->swapin_count += tsk->delays->swapin_count;
    + spin_unlock(&tsk->delays->lock);
    +
    + return 0;
    +}
    Index: linux-2.6.17-rc1/kernel/taskstats.c
    ===================================================================
    --- linux-2.6.17-rc1.orig/kernel/taskstats.c 2006-04-21 20:29:22.000000000 -0400
    +++ linux-2.6.17-rc1/kernel/taskstats.c 2006-04-21 20:40:03.000000000 -0400
    @@ -18,6 +18,7 @@

    #include <linux/kernel.h>
    #include <linux/taskstats_kern.h>
    +#include <linux/delayacct.h>
    #include <net/genetlink.h>
    #include <asm/atomic.h>

    @@ -119,7 +120,9 @@ static int fill_pid(pid_t pid, struct ta
    * goto err;
    */

    -err:
    + rc = delayacct_add_tsk(stats, tsk);
    +
    + /* Define err: label here if needed */
    put_task_struct(tsk);
    return rc;

    @@ -151,6 +154,10 @@ static int fill_tgid(pid_t tgid, struct
    * break;
    */

    + rc = delayacct_add_tsk(stats, tsk);
    + if (rc)
    + break;
    +
    } while_each_thread(first, tsk);
    read_unlock(&tasklist_lock);

    Index: linux-2.6.17-rc1/init/Kconfig
    ===================================================================
    --- linux-2.6.17-rc1.orig/init/Kconfig 2006-04-21 20:29:22.000000000 -0400
    +++ linux-2.6.17-rc1/init/Kconfig 2006-04-21 20:40:03.000000000 -0400
    @@ -164,6 +164,7 @@ config TASKSTATS

    config TASK_DELAY_ACCT
    bool "Enable per-task delay accounting (EXPERIMENTAL)"
    + depends on TASKSTATS
    help
    Collect information on time spent by a task waiting for system
    resources like cpu, synchronous block I/O completion and swapping
    Index: linux-2.6.17-rc1/include/linux/taskstats.h
    ===================================================================
    --- linux-2.6.17-rc1.orig/include/linux/taskstats.h 2006-04-21 20:31:11.000000000 -0400
    +++ linux-2.6.17-rc1/include/linux/taskstats.h 2006-04-21 20:45:17.000000000 -0400
    @@ -35,7 +35,53 @@ struct taskstats {

    /* Version 1 */

    - int filler_avoids_empty_struct_warnings;
    + /* Delay accounting fields start
    + *
    + * All values, until comment "Delay accounting fields end" are
    + * available only if delay accounting is enabled, even though the last
    + * few fields are not delays
    + *
    + * xxx_count is the number of delay values recorded
    + * xxx_delay_total is the corresponding cumulative delay in nanoseconds
    + *
    + * xxx_delay_total wraps around to zero on overflow
    + * xxx_count incremented regardless of overflow
    + */
    +
    + /* Delay waiting for cpu, while runnable
    + * count, delay_total NOT updated atomically
    + */
    + __u64 cpu_count;
    + __u64 cpu_delay_total;
    +
    + /* Following four fields atomically updated using task->delays->lock */
    +
    + /* Delay waiting for synchronous block I/O to complete
    + * does not account for delays in I/O submission
    + */
    + __u64 blkio_count;
    + __u64 blkio_delay_total;
    +
    + /* Delay waiting for page fault I/O (swap in only) */
    + __u64 swapin_count;
    + __u64 swapin_delay_total;
    +
    + /* cpu "wall-clock" running time
    + * On some architectures, value will adjust for cpu time stolen
    + * from the kernel in involuntary waits due to virtualization.
    + * Value is cumulative, in nanoseconds, without a corresponding count
    + * and wraps around to zero silently on overflow
    + */
    + __u64 cpu_run_real_total;
    +
    + /* cpu "virtual" running time
    + * Uses time intervals seen by the kernel i.e. no adjustment
    + * for kernel's involuntary waits due to virtualization.
    + * Value is cumulative, in nanoseconds, without a corresponding count
    + * and wraps around to zero silently on overflow
    + */
    + __u64 cpu_run_virtual_total;
    + /* Delay accounting fields end */
    };


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