Date: Sat, 5 Mar 2005 14:06:23 +0100 (CET) From: Antoine Brodin <antoine.brodin@laposte.net> To: FreeBSD-gnats-submit@FreeBSD.org Subject: kern/78444: sched_ule: doesn't keep track of the sleep time of a process Message-ID: <200503051306.j25D6NFG000989@barton.dreadbsd.org> Resent-Message-ID: <200503051310.j25DADlk032761@freefall.freebsd.org>
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>Number: 78444
>Category: kern
>Synopsis: sched_ule: doesn't keep track of the sleep time of a process
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sat Mar 05 13:10:13 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator: Antoine Brodin
>Release: FreeBSD 6.0-CURRENT i386
>Organization:
none
>Environment:
System: FreeBSD barton.dreadbsd.org 6.0-CURRENT FreeBSD 6.0-CURRENT #1: Thu Mar 3 15:04:32 CET 2005 antoine@barton.dreadbsd.org:/usr/obj/usr/src/sys/BARTON i386
>Description:
When using the sched_ule scheduler, the sleep time of a process isn't
computed.
kg_slptime is zeroed during the ksegrp creation and after that, it's
never modified.
In sched_ule.c, something named kg_slptime is manipulated but it's not
the sleep time of a process: there's the macro
#define kg_slptime kg_sched->skg_slptime
It represents an history of the process's sleep and not a sleep time
and it would be bogus to use it as the sleep time.
Side effects: swapout doesn't work as intended: a process can never be
swaped out since its sleep time is 0 and is below swap_idle_threshold1.
>How-To-Repeat:
Use ps:
$ ps -o sl
SL
0
0
0
0
0
0
0
0
0
0
0
0
>Fix:
Having a lightweight schedcpu routine running every hz ticks like in
sched_4bsd ?
The problem is that such a routine would use a O(n) algorithm and would
penalize quite unnecessarily sched_ule.
Another idea: add a sched_slptime routine in sched_ule.c for swapout
and fill_kinfo_thread to use ?
add something like this to sched_ule.c:
%%
u_int
sched_slptime(struct ksegrp *kg)
{
struct thread *td;
u_int slptime = UINT_MAX;
u_int hzticks;
PROC_LOCK_ASSERT(kg->kg_proc, MA_OWNED);
mtx_assert(&sched_lock, MA_OWNED);
FOREACH_THREAD_IN_GROUP(kg, td) {
if (td->td_slptime) {
hzticks = ticks - td->td_slptime;
slptime = min(slptime, hzticks);
} else
return (0);
}
return (slptime / hz);
}
%%
add something like this to sched_4bsd.c:
%%
u_int
sched_slptime(struct ksegrp *kg)
{
return (kg->kg_slptime);
}
%%
add something like this to sched.h:
%%
u_int sched_slptime(struct ksegrp *kg);
%%
and use sched_slptime(kg) in vm_glue.c and kern_proc.c instead of
kg->kg_slptime
>Release-Note:
>Audit-Trail:
>Unformatted:
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