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RE: personal webpage for L4-Hurd
From: |
Volkmar Uhlig |
Subject: |
RE: personal webpage for L4-Hurd |
Date: |
Thu, 23 Nov 2000 20:41:11 +0100 |
> > 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