linux-kernel - Re: [RFC][PATCH 4/7] sched: Replace sd_busy/nr_busy_cpus with sched_domain

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Message-ID: <20160517105204.GA9986@linux.vnet.ibm.com>
Date:	Tue, 17 May 2016 16:22:04 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Michael Neuling <mikey@...ling.org>,
	Matt Fleming <matt@...eblueprint.co.uk>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, clm@...com, mgalbraith@...e.de,
	tglx@...utronix.de, fweisbec@...il.com, anton@...ba.org,
	oliver <oohall@...il.com>,
	"Shreyas B. Prabhu" <shreyas@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH 4/7] sched: Replace sd_busy/nr_busy_cpus with
 sched_domain_shared

> 
> Maybe even something like so; which would make Power <= 6 use the
> default topology and result in a shared LLC between the on package cores
> etc..
> 
> Power7 is then special for not having a shared L3 but having the
> asymmetric SMT thing and Power8 again gains the shared L3 while
> retaining the asymmetric SMT stuff.


Asymmetric SMT is only for Power 7. Its not enabled for Power 8.
On Power8, if there are only 2 active threads assume thread 0 and thread
4 running in smt 8 mode, it would internally run as if running in smt 2
mode without any scheduler tweaks. (This is unlike power 7).

-- 
Thanks and Regards
Srikar Dronamraju