Re: [RFD] CAT user space interface revisited

From	Chao Peng <chao.p.peng@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [RFD] CAT user space interface revisited
Date	2015-11-24 09:40 +0100
Message-ID	<qyhiN-5GD-1@gated-at.bofh.it> (permalink)
References	<qwfEv-6Cj-21@gated-at.bofh.it> <qwl7c-1Xq-19@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, Nov 18, 2015 at 10:01:54PM -0200, Marcelo Tosatti wrote:
> > 	tglx
> 
> Again: you don't need to look into the MSR table and relate it 
> to tasks if you store the data as:
> 
> 	task group 1 = {
> 			reservation-1 = {size = 80Kb, type = data, socketmask = 0xffff},
> 			reservation-2 = {size = 100Kb, type = code, socketmask = 0xffff}
> 	}
> 	
> 	task group 2 = {
> 			reservation-1 = {size = 80Kb, type = data, socketmask = 0xffff},
> 			reservation-3 = {size = 200Kb, type = code, socketmask = 0xffff}
> 	}
> 
> Task group 1 and task group 2 share reservation-1.

Because there is only size but not CBM position info, I guess for
different reservations they will not overlap each other, right?

Personally I like this way of exposing minimal information to userspace.
I can think it working well except for one concern of losing flexibility:

For instance, there is a box for which the full CBM is 0xfffff. After
cache reservation creating/freeing for a while we then have reservations:

reservation1: 0xf0000
reservation2: 0x00ff0

Now people want to request a reservation which size is 0xff, so how
will kernel do at this time? It could return just error or do some
moving/merging (e.g. for reservation2: 0x00ff0 => 0x0ff00) and then
satisfy the request. But I don't know if the moving/merging will cause
delay for tasks that is using it.

Thanks,
Chao
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Thread

[RFD] CAT user space interface revisited Thomas Gleixner <tglx@linutronix.de> - 2015-11-18 19:30 +0100
  Re: [RFD] CAT user space interface revisited Luiz Capitulino <lcapitulino@redhat.com> - 2015-11-18 20:40 +0100
    RE: [RFD] CAT user space interface revisited "Auld, Will" <will.auld@intel.com> - 2015-11-18 21:00 +0100
  Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-18 23:40 +0100
    Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-19 01:40 +0100
      Re: [RFD] CAT user space interface revisited Thomas Gleixner <tglx@linutronix.de> - 2015-11-19 09:40 +0100
        Re: [RFD] CAT user space interface revisited Luiz Capitulino <lcapitulino@redhat.com> - 2015-11-19 14:50 +0100
        Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-20 17:40 +0100
    Re: [RFD] CAT user space interface revisited Thomas Gleixner <tglx@linutronix.de> - 2015-11-19 09:20 +0100
  Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-19 01:20 +0100
    Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-19 02:10 +0100
      Re: [RFD] CAT user space interface revisited Thomas Gleixner <tglx@linutronix.de> - 2015-11-19 10:10 +0100
        Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-19 23:30 +0100
          Re: [RFD] CAT user space interface revisited Thomas Gleixner <tglx@linutronix.de> - 2015-11-20 09:00 +0100
            Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-20 20:30 +0100
      Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-19 21:40 +0100
    Re: [RFD] CAT user space interface revisited Thomas Gleixner <tglx@linutronix.de> - 2015-11-19 10:10 +0100
    Re: [RFD] CAT user space interface revisited Chao Peng <chao.p.peng@linux.intel.com> - 2015-11-24 09:40 +0100
      Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-25 23:10 +0100
  Re: [RFD] CAT user space interface revisited Chao Peng <chao.p.peng@linux.intel.com> - 2015-11-24 08:40 +0100
    Re: [RFD] CAT user space interface revisited Marcelo Tosatti <mtosatti@redhat.com> - 2015-11-25 23:10 +0100

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