linux-kernel - Re: [PATCH v5 6/9] ACPI/PPTT: Add topology parsing code

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: <CAJZ5v0hBZQ-vYbobOYtKFVg9hAtUo4GU==napcJ-btQhMvn+5g@mail.gmail.com>
Date:   Thu, 14 Dec 2017 00:09:54 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Jeremy Linton <jeremy.linton@....com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>, jhugo@...eaurora.org,
        wangxiongfeng2@...wei.com, Jonathan.Zhang@...ium.com,
        Al Stone <ahs3@...hat.com>, Jayachandran.Nair@...ium.com,
        austinwc@...eaurora.org, Len Brown <lenb@...nel.org>
Subject: Re: [PATCH v5 6/9] ACPI/PPTT: Add topology parsing code

On Thu, Dec 14, 2017 at 12:06 AM, Jeremy Linton <jeremy.linton@....com> wrote:
> Hi,
>
>
> On 12/13/2017 04:28 PM, Rafael J. Wysocki wrote:
>>
>> On Wed, Dec 13, 2017 at 6:38 PM, Lorenzo Pieralisi
>> <lorenzo.pieralisi@....com> wrote:
>>>
>>> On Tue, Dec 12, 2017 at 10:13:08AM -0600, Jeremy Linton wrote:
>>>>
>>>> Hi,
>>>>
>>>> First, thanks for taking a look at this.
>>>>
>>>> On 12/11/2017 07:12 PM, Rafael J. Wysocki wrote:
>>>>>
>>>>> On Friday, December 1, 2017 11:23:27 PM CET Jeremy Linton wrote:
>>>>>>
>>>>>> The PPTT can be used to determine the groupings of CPU's at
>>>>>> given levels in the system. Lets add a few routines to the PPTT
>>>>>> parsing code to return a unique id for each unique level in the
>>>>>> processor hierarchy. This can then be matched to build
>>>>>> thread/core/cluster/die/package/etc mappings for each processing
>>>>>> element in the system.
>>>>>>
>>>>>> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
>>>>>
>>>>>
>>>>> Why can't this be folded into patch [2/9]?
>>>>
>>>>
>>>> It can, and I will be happy squash it.
>>>>
>>>> It was requested that the topology portion of the parser be split
>>>> out back in v3.
>>>>
>>>> https://www.spinics.net/lists/linux-acpi/msg78487.html
>>>
>>>
>>> I asked to split cache/topology since I am not familiar with cache
>>> code and Sudeep - who looks after the cache code - won't be able
>>> to review this series in time for v4.16.
>>
>>
>> OK, so why do we need it in 4.16?
>
>
> I think its more case of as soon as possible. That is because there are
> machines where the topology is completely incorrect due to assumptions the
> kernel makes based on registers that aren't defined for that purpose (say
> describing which cores are in a physical socket, or LLC's attached to
> interconnects or memory controllers).
>
> This incorrect topology information is reported to things like the kernel
> scheduler, which then makes poor scheduling decisions resulting in
> sub-optimal system performance.
>
> This patchset (and ACPI 6.2) clears up a lot of those problems.

As long as the ACPI tables are as expected that is, I suppose?

Anyway, fair enough, but I don't want to rush it in.

Thanks,
Rafael