linux-kernel - Re: [RFC] CPU hard limits

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]

Message-ID: <6599ad830906050251h18f4e037h182f61aa80a5b046@mail.gmail.com>
Date:	Fri, 5 Jun 2009 02:51:18 -0700
From:	Paul Menage <menage@...gle.com>
To:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>
Cc:	bharata@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Avi Kivity <avi@...hat.com>, kvm@...r.kernel.org,
	Linux Containers <containers@...ts.linux-foundation.org>,
	Herbert Poetzl <herbert@...hfloor.at>
Subject: Re: [RFC] CPU hard limits

On Fri, Jun 5, 2009 at 2:48 AM, Dhaval Giani<dhaval@...ux.vnet.ibm.com> wrote:
>> > Now if 11th group with same shares comes in, then each group will now
>> > get 9% of CPU and that 10% guarantee breaks.
>>
>> So you're trying to guarantee 11 cgroups that they can each get 10% of
>> the CPU? That's called over-committing, and while there's nothing
>> wrong with doing that if you're confident that they'll not all need
>> their 10% at the same time, there's no way to *guarantee* them all
>> 10%. You can guarantee them all 9% and hope the extra 1% is spare for
>> those that need it (over-committing), or you can guarantee 10 of them
>> 10% and give the last one 0 shares.
>>
>> How would you propose to guarantee 11 cgroups each 10% of the CPU
>> using hard limits?
>>
>
> You cannot guarantee 10% to 11 groups on any system (unless I am missing
> something). The sum of guarantees cannot exceed 100%.

That's exactly my point. I was trying to counter Bharata's statement, which was:

> > Now if 11th group with same shares comes in, then each group will now
> > get 9% of CPU and that 10% guarantee breaks.

which seemed to be implying that this was a drawback of using shares
to implement guarantees.

Paul
--
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/