linux-kernel - Re: [PATCH 5/9] x86/intel_rdt: Add new cgroup and Class of service management

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Message-ID: <20150802163157.GB32599@mtj.duckdns.org>
Date:	Sun, 2 Aug 2015 12:31:57 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Vikas Shivappa <vikas.shivappa@...el.com>
Cc:	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
	tglx@...utronix.de, mingo@...nel.org, peterz@...radead.org,
	matt.fleming@...el.com, will.auld@...el.com,
	glenn.p.williamson@...el.com, kanaka.d.juvva@...el.com
Subject: Re: [PATCH 5/9] x86/intel_rdt: Add new cgroup and Class of service
 management

Hello, Vikas.

On Fri, Jul 31, 2015 at 09:24:58AM -0700, Vikas Shivappa wrote:
> Yes today we dont have an alternative interface - but we can always build
> one. We simply dont have it because till now Linux kernel just tolerated the
> degradation that could have occured by cache contention and this is the
> first interface we are building.

But we're doing it the wrong way around.  You can do most of what
cgroup interface can do with systemcall-like interface with some
inconvenience.  The other way doesn't really work.  As I wrote in the
other reply, cgroups is a horrible programmable interface and we don't
want individual applications to interact with it directly and CAT's
use cases most definitely include each application programming its own
cache mask.  Let's build something which is simple and can be used
easily first.  If this turns out to be widely useful and an overall
management capability over it is wanted, we can consider cgroups then.

Thanks.

-- 
tejun
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