From: Shivappa Vikas <vikas.shivappa@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Shivappa Vikas <vikas.shivappa@intel.com>,
Vikas Shivappa <vikas.shivappa@linux.intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com,
mingo@kernel.org, peterz@infradead.org, ravi.v.shankar@intel.com,
tony.luck@intel.com, fenghua.yu@intel.com,
h.peter.anvin@intel.com
Subject: Re: [PATCH 6/8] x86/intel_rdt/mba: Add info directory files for MBA
Date: Mon, 23 Jan 2017 11:45:41 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.10.1701231121460.3301@vshiva-Udesk> (raw)
In-Reply-To: <alpine.DEB.2.20.1701181005360.3464@nanos>
On Wed, 18 Jan 2017, Thomas Gleixner wrote:
> On Tue, 17 Jan 2017, Shivappa Vikas wrote:
>> On Mon, 16 Jan 2017, Thomas Gleixner wrote:
>>
>>> On Tue, 10 Jan 2017, Vikas Shivappa wrote:
>>>
>>>> Add the files in info directory for MBA.
>>>> The files in the info directory are as follows :
>>>> - num_closids: max number of closids for MBA which represents the max
>>>> class of service user can configure.
>>>> - max_thrtl_by: the max throttle by values.
>>>>
>>>> Throttle by can have a linear scale and non linear scale. In linear
>>>> scale, if a throttle_by value is 40%, it means that the memory b/w is
>>>> throttled 'by' 40% or in other words a max of 60% b/w is allowed to
>>>> pass. In non-linear scale, the throttle_by values are in 2^n
>>>> granularity. The h/w does not guarantee a curve of actual throttle w.r.t
>>>> the configured values. But if a throttle_by value of x > y, then x is
>>>> guaranteed to throttle more b/w than y.
>>>
>>> This is ambigous because that is only correct when the effective values are
>>> different. x=11 and y=12 with a granularity of 10 are resulting in the same
>>> throttling.
>>
>> The x and y are actual values written which i will spell out. The assumption
>> is that only correct values are input though because we filterout the values
>> which dont follow granularity, meaning return -EINVAL when someone tries to
>> write 11 when granularity is 10. This was with the idea thats its easier for
>> the user to understand whats actually written. Woudl that be reasonable or
>> does it need a change ?
>> (Although the h/w does like you say , we can do a msr write for 11 etc ..)
>
>
>>>> +/* rdtgroup information files for MBE. */
>>>> +static struct rftype res_mbe_info_files[] = {
>>>> + {
>>>> + .name = "num_closids",
>>>> + .mode = 0444,
>>>> + .kf_ops = &rdtgroup_kf_single_ops,
>>>> + .seq_show = rdt_num_closids_show,
>>>> + },
>>>> + {
>>>> + .name = "max_thrtl_by",
>>>
>>> You surely could not come up with a more cryptic file name, right? What's
>>> so wrong with spelling out throttle? And the whole '_by' postfix here and
>>> on the other files is pointless as well.
>>
>> This is due to the issue i mention in reply to 1/8.. Can be changed to
>
> Err no. max_thrtl_by has nothing to do with 1/8. Of course you want to
> expose the hardware information.
>
> What's wrong with spelling out throttle and remove the '_by':
>
> max_throttle
Always was under the impression max_throttle by default means the max b/w thats
allowed. (if max_throttle is 90, user would think 90% is whats the most allowed
to pass..). But this is really the delay value which was implemented which
means the % of bytes that are 'not' allowed to pass (so 90 means , that 90% is whats
restricted and 10 is what is allowed).
Thanks,
Vikas
>
> That is readable, understandable and matches the documentation in the SDM.
>
> It's not that hard.
>
> Thanks,
>
> tglx
>
>
next prev parent reply other threads:[~2017-01-23 19:45 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-10 19:33 [PATCH 0/8 V1] x86/intel_rdt: Memory b/w Allocation support Vikas Shivappa
2017-01-10 19:33 ` [PATCH 1/8] Documentation, x86: Documentation for Intel Mem b/w allocation user interface Vikas Shivappa
2017-01-16 13:43 ` Thomas Gleixner
2017-01-18 0:51 ` Shivappa Vikas
2017-01-18 9:01 ` Thomas Gleixner
2017-01-23 18:57 ` Shivappa Vikas
2017-01-23 19:01 ` Thomas Gleixner
2017-01-24 22:10 ` Shivappa Vikas
2017-01-10 19:33 ` [PATCH 2/8] x86/intel_rdt/mba: Generalize the naming to get ready for MBA Vikas Shivappa
2017-01-16 13:45 ` Thomas Gleixner
2017-01-10 19:33 ` [PATCH 3/8] x86/intel_rdt/mba: Improvements to handle more RDT resources like MBA Vikas Shivappa
2017-01-16 13:54 ` Thomas Gleixner
2017-01-18 0:53 ` Shivappa Vikas
2017-01-18 9:05 ` Thomas Gleixner
2017-01-10 19:33 ` [PATCH 4/8] x86/intel_rdt/mba: Memory b/w allocation feature detect Vikas Shivappa
2017-01-16 13:59 ` Thomas Gleixner
2017-01-16 14:41 ` Peter Zijlstra
2017-01-16 16:16 ` Thomas Gleixner
2017-01-10 19:33 ` [PATCH 5/8] x86/intel_rct/mba: Add MBA structures and initialize MBA Vikas Shivappa
2017-01-16 14:06 ` Thomas Gleixner
2017-01-18 0:56 ` Shivappa Vikas
2017-01-10 19:33 ` [PATCH 6/8] x86/intel_rdt/mba: Add info directory files for MBA Vikas Shivappa
2017-01-16 14:14 ` Thomas Gleixner
2017-01-18 1:02 ` Shivappa Vikas
2017-01-18 9:08 ` Thomas Gleixner
2017-01-23 19:45 ` Shivappa Vikas [this message]
2017-01-10 19:33 ` [PATCH 7/8] x86/intel_rdt/mba: Add schemata file support " Vikas Shivappa
2017-01-16 16:07 ` Thomas Gleixner
2017-01-18 1:03 ` Shivappa Vikas
2017-01-10 19:33 ` [PATCH 8/8] x86/intel_rdt: rmdir,umount and hotcpu updates " Vikas Shivappa
2017-01-16 16:13 ` Thomas Gleixner
2017-01-23 20:18 ` Shivappa Vikas
2017-02-17 19:58 [PATCH 0/8 V2] x86/intel_rdt: Intel Memory bandwidth allocation Vikas Shivappa
2017-02-17 19:58 ` [PATCH 6/8] x86/intel_rdt/mba: Add info directory files for MBA Vikas Shivappa
2017-03-01 16:05 ` Thomas Gleixner
2017-03-10 23:26 ` Shivappa Vikas
2017-04-03 21:57 [PATCH 0/8 V3] x86/intel_rdt: Intel Memory bandwidth allocation Vikas Shivappa
2017-04-03 21:57 ` [PATCH 6/8] x86/intel_rdt/mba: Add info directory files for MBA Vikas Shivappa
2017-04-08 0:33 [PATCH 0/8 V4] x86/intel_rdt: Intel Memory bandwidth allocation Vikas Shivappa
2017-04-08 0:33 ` [PATCH 6/8] x86/intel_rdt/mba: Add info directory files for MBA Vikas Shivappa
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