linux-kernel - Re: [PATCH 3/3] sched, fair: Stop searching for tasks in newidle balance if there are runnable tasks

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:	Thu, 24 Apr 2014 20:33:26 -0700
From:	Jason Low <jason.low2@...com>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, daniel.lezcano@...aro.org,
	alex.shi@...aro.org, preeti@...ux.vnet.ibm.com,
	vincent.guittot@...aro.org, morten.rasmussen@....com, aswin@...com,
	chegu_vinod@...com
Subject: Re: [PATCH 3/3] sched, fair: Stop searching for tasks in newidle
 balance if there are runnable tasks

On Fri, 2014-04-25 at 04:45 +0200, Mike Galbraith wrote:
> On Thu, 2014-04-24 at 18:52 +0200, Peter Zijlstra wrote: 
> > On Thu, Apr 24, 2014 at 09:43:09AM -0700, Jason Low wrote:
> > > If the below patch is what you were referring to, I believe this
> > > can help too. This was also something that I was testing out before
> > > we went with those patches which compares avg_idle with idle balance
> > > cost. I recall seeing somewhere around a +7% performance improvement
> > > in at least least 1 of the AIM7 workloads. I can do some more testing
> > > with this.
> > 
> > Yes, exactly that.
> > 
> > I can't remember the details, but I suspect we feared the less agressive
> > idle balance due to that patch (it will only pull a single task, instead
> > of multiple) would cause more idle_balance invocations and thereby
> > decrease throughput.
> > 
> > So I suppose something with _many_ bursty threads which leads to severe
> > inequalities would be the workload to trigger that.
> > 
> > Not sure we've ever seen that.. maybe Mike remembers, he seems to have a
> > head for such details.
> 
> I don't recall ever seeing such.

Hmmm, could commit: 1b9508f6831e (sched: Rate-limit newidle) be related
to what Peter's referring to? The patch mentioned that the rate-limit
benefited "sysbench oltp".


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/