RE: personal webpage for L4-Hurd

[Volkmar Uhlig]

> > you write on your web-page:
> > "One thing which I find cannot be realized in current L4 is
> that it doesn't
> > provide sufficient information on elapsed time. This is
> necessary especially
> > for profiling, but L4 doesn't tell how amount of time is
> used for a certain
> > thread (e.g. system time in Mach). I think the L4 API
> should be extended."
> >
> > That is not true. Have a look at the thread_schedule
> syscall which provides
> > the time consumed by a thread.
>
>   Thanks for your suggestion, but I don't think so. In GNU Mach, this
> is defined in include/mach/thread_info.h:
>
> struct thread_basic_info {
>         time_value_t    user_time;      /* user run time */
>         time_value_t    system_time;    /* system run time */
>         integer_t       cpu_usage;      /* scaled cpu usage
> percentage */
>         integer_t       base_priority;  /* base scheduling priority */
>         integer_t       cur_priority;   /* current scheduling
> priority */
>         integer_t       run_state;      /* run state (see below) */
>         integer_t       flags;          /* various flags (see
> below) */
>         integer_t       suspend_count;  /* suspend count for thread */
>         integer_t       sleep_time;     /* number of seconds
> that thread
>                                            has been sleeping */
>         time_value_t    creation_time;  /* time stamp of creation */
> };
>
> As you see, Mach distinguishes user-level run time from system-level
> run time consumed by each thread. AFAIK, thread_schedule returns only
> one run time value (it is not clear whether the value should be total
> run time or user-level run time, though). This means that you cannot
> implement ITIMER_PROF or ITIMER_VIRTUAL in Unix correctly.

The L4 kernel does not account kernel time (e.g. the transfer time of an IPC
is not part of the timeout) because we assume kernel time is to short to be
accounted. Speaking of Unix semantics: this should not be time spend in L4
kernel mode but time spend in the Unix user level servers.

Volkmar

---
Dipl. Inf. Volkmar Uhlig,
System Architecture Group, University of Karlsruhe, Germany
mailto:address@hidden, phone: +49 (172) 352-8285