linux-kernel - Re: [RFC PATCH 3/4] sched/topology: remove smt

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 for Android: free password hash cracker in your pocket

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

Date:   Wed, 5 Sep 2018 01:50:29 -0700
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 3/4] sched/topology: remove smt_gain

* Vincent Guittot <vincent.guittot@...aro.org> [2018-09-05 09:36:42]:

> >
> > I dont know of any systems that have come with single threaded and
> > multithreaded. However some user can still offline few threads in a core
> > while leaving other cores untouched. I dont really know why somebody
> > would want to do it.  For example, some customer was toying with SMT 3
> > mode in a SMT 8 power8 box.
> 
> In this case, it means that we have the same core capacity whatever
> the number of CPUs
> and a core with SMT 3 will be set with the same compute capacity as
> the core with SMT 8.
> Does it still make sense ?
> 

To me it make sense atleast from  a power 8 perspective, because SMT 1 >
SMT 2 > SMT 4 > SMT8. So if one core is configured for SMT 2 and other
core is configured for SMT4; all threads being busy, the  individual
threads running on SMT2 core will complete more work than SMT 4 core
threads.

-- 
Thanks and Regards
Srikar Dronamraju