linux-kernel - Re: [PATCH v2 11/11] sched: replace capacity by activity

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 30 May 2014 08:34:02 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Mike Galbraith <efault@....de>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v2 11/11] sched: replace capacity by activity

On Thu, May 29, 2014 at 09:56:24PM +0200, Vincent Guittot wrote:
> On 29 May 2014 16:02, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Fri, May 23, 2014 at 05:53:05PM +0200, Vincent Guittot wrote:
> >> @@ -6052,8 +6006,8 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
> >>                * with a large weight task outweighs the tasks on the system).
> >>                */
> >>               if (prefer_sibling && sds->local &&
> >> -                 sds->local_stat.group_has_capacity)
> >> -                     sgs->group_capacity = min(sgs->group_capacity, 1U);
> >> +                 sds->local_stat.group_capacity > 0)
> >> +                     sgs->group_capacity = min(sgs->group_capacity, 1L);
> >>
> >>               if (update_sd_pick_busiest(env, sds, sg, sgs)) {
> >>                       sds->busiest = sg;
> >> @@ -6228,7 +6182,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
> >>                * have to drop below capacity to reach cpu-load equilibrium.
> >>                */
> >>               load_above_capacity =
> >> -                     (busiest->sum_nr_running - busiest->group_capacity);
> >> +                     (busiest->sum_nr_running - busiest->group_weight);
> >>
> >>               load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
> >>               load_above_capacity /= busiest->group_power;
> >
> > I think you just broke PREFER_SIBLING here..
> 
> you mean by replacing the capacity which was reflecting the number of
> core for SMT by the group_weight ?

Right to in the first hunk we lower group_capacity to 1 when prefer_sibling,
then in the second hunk, you replace that group_capacity usage with
group_weight.

With the end result that prefer_sibling is now ineffective.

That said, I fudged the prefer_sibling usage into the capacity logic,
mostly because I could and it was already how the SMT stuff was working.
But there is no reason we should continue to intertwine these two
things.

So I think it would be good to have a patch that implements
prefer_sibling on nr_running separate from the existing capacity bits,
and then convert the remaining capacity bits to utilization (or activity
or whatever you did call it, see Morton's comments etc.).



Content of type "application/pgp-signature" skipped