Messages in this thread | | | Subject | Re: [patch] sched, cgroups: fix MIN_SHARES on 64 bit boxen | From | Peter Zijlstra <> | Date | Sat, 04 Jun 2011 13:24:49 +0200 |
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On Sat, 2011-06-04 at 11:29 +0200, Mike Galbraith wrote: > c8b28116 claimed to have no user-visible effect, but allows setting cpu.shares > to < MIN_SHARES, which the user then indeed sees. > > Signed-off-by: Mike Galbraith <efault@gmx.de> > --- > kernel/sched.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Index: linux-2.6/kernel/sched.c > =================================================================== > --- linux-2.6.orig/kernel/sched.c > +++ linux-2.6/kernel/sched.c > @@ -292,7 +292,7 @@ static DEFINE_SPINLOCK(task_group_lock); > * (The default weight is 1024 - so there's no practical > * limitation from this.) > */ > -#define MIN_SHARES 2 > +#define MIN_SHARES (scale_load(2)) > #define MAX_SHARES (1UL << (18 + SCHED_LOAD_RESOLUTION)) > > static int root_task_group_load = ROOT_TASK_GROUP_LOAD;
Hurm, but that destroys most of the gains from that patch, the whole point was being able to have finer graunlarities, but now calc_cfs_shares() and effective_load() are clipped the coarse granularity.
So maybe explicitly change the MIN_SHARES usage in sched_group_set_shares(). That wants to become a clamp user anyway, something like:
shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
That way MAX_SHARES can also loose its SCHED_LOAD_RESOLUTION factor and bring is back in line with MIN_SHARES.
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