On Friday 14 April 2006 13:16, Al Boldi wrote:
> Can you try the attached mem-eater passing it the number of kb to be eaten.
>
> i.e. '# while :; do ./eatm 9999 ; done'
>
> This will print the number of bytes eaten and the timing in ms.
>
> Assuming timeslice=100, adjust the number of kb to be eaten such that the
> timing will be less than timeslice (something like 60ms). Switch to
> another vt and start another eatm w/ the number of kb yielding more than
> timeslice (something like 140ms). This eatm should starve completely after
> exceeding timeslice.
>
> This problem also exists in mainline, but it is able to break out of it to
> some extent. Setting eatm kb to a timing larger than timeslice does not
> exhibit this problem.
Thanks for bringing this to my attention. A while back I had different
management of forked tasks and merged it with PF_NONSLEEP. Since then I've
changed the management of NONSLEEP tasks and didn't realise it had adversely
affected the accounting of forking tasks. This patch should rectify it.
Thanks!
---
include/linux/sched.h | 1 +
kernel/sched.c | 9 ++++++---
2 files changed, 7 insertions(+), 3 deletions(-)
Index: linux-2.6.16-ck5/include/linux/sched.h
===================================================================
--- linux-2.6.16-ck5.orig/include/linux/sched.h 2006-04-15 16:32:18.000000000 +1000
+++ linux-2.6.16-ck5/include/linux/sched.h 2006-04-15 16:34:36.000000000 +1000
@@ -961,6 +961,7 @@ static inline void put_task_struct(struc
#define PF_SWAPWRITE 0x01000000 /* Allowed to write to swap */
#define PF_NONSLEEP 0x02000000 /* Waiting on in kernel activity */
#define PF_ISOREF 0x04000000 /* SCHED_ISO task has used up quota */
+#define PF_FORKED 0x08000000 /* Task just forked another process */
/*
* Only the _current_ task can read/write to tsk->flags, but other
Index: linux-2.6.16-ck5/kernel/sched.c
===================================================================
--- linux-2.6.16-ck5.orig/kernel/sched.c 2006-04-15 16:32:18.000000000 +1000
+++ linux-2.6.16-ck5/kernel/sched.c 2006-04-15 16:34:35.000000000 +1000
@@ -18,7 +18,7 @@
* 2004-04-02 Scheduler domains code by Nick Piggin
* 2006-04-02 Staircase scheduling policy by Con Kolivas with help
* from William Lee Irwin III, Zwane Mwaikambo & Peter Williams.
- * Staircase v15
+ * Staircase v15_test2
*/
#include <linux/mm.h>
@@ -809,6 +809,9 @@ static inline void recalc_task_prio(task
else
sleep_time = 0;
+ if (unlikely(p->flags & PF_FORKED))
+ sleep_time = 0;
+
/*
* If we sleep longer than our running total and have not set the
* PF_NONSLEEP flag we gain a bonus.
@@ -847,7 +850,7 @@ static void activate_task(task_t *p, run
p->time_slice = p->slice % rr ? : rr;
if (!rt_task(p)) {
recalc_task_prio(p, now);
- p->flags &= ~PF_NONSLEEP;
+ p->flags &= ~(PF_NONSLEEP | PF_FORKED);
p->systime = 0;
p->prio = effective_prio(p);
}
@@ -1464,7 +1467,7 @@ void fastcall wake_up_new_task(task_t *p
/* Forked process gets no bonus to prevent fork bombs. */
p->bonus = 0;
- current->flags |= PF_NONSLEEP;
+ current->flags |= PF_FORKED;
if (likely(cpu == this_cpu)) {
activate_task(p, rq, 1);
--
-ck
-
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