From: Andrew Jones <drjones@redhat.com>
To: Sudeep Holla <sudeep.holla@arm.com>
Cc: Jeremy Linton <jeremy.linton@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, ard.biesheuvel@linaro.org,
shunyong.yang@hxt-semitech.com, yu.zheng@hxt-semitech.com,
catalin.marinas@arm.com, will.deacon@arm.com
Subject: Re: [PATCH] arm64: acpi: reenumerate topology ids
Date: Fri, 29 Jun 2018 13:55:39 +0200 [thread overview]
Message-ID: <20180629115539.w7lgjy2bmucgz7gm@kamzik.brq.redhat.com> (raw)
In-Reply-To: <20180629114227.4noje2kx3lcjbcpd@kamzik.brq.redhat.com>
On Fri, Jun 29, 2018 at 01:42:27PM +0200, Andrew Jones wrote:
> On Fri, Jun 29, 2018 at 11:53:34AM +0100, Sudeep Holla wrote:
> > On Thu, Jun 28, 2018 at 12:12:00PM -0500, Jeremy Linton wrote:
> > > Hi,
> > >
> > > On 06/28/2018 11:30 AM, Sudeep Holla wrote:
> >
> > [...]
> >
> > > >I am not sure if we can ever guarantee that DT and ACPI will get the
> > > >same ids whatever counter we use as it depends on the order presented in
> > > >the firmware(DT or ACPI). So I am not for generating ids for core and
> > > >threads in that way.
> > > >
> > > >So I would like to keep it simple and just have this counters for
> > > >package ids as demonstrated in Shunyong's patch.
> > >
> > > So, currently on a non threaded system, the core id's look nice because they
> > > are just the ACPI ids. Its the package id's that look strange, we could just
> > > fix the package ids, but on threaded machines the threads have the nice acpi
> > > ids, and the core ids are then funny numbers. So, I suspect that is driving
> > > this as much as the strange package ids.
> > >
> >
> > Yes, I know that and that's what made be look at topology_get_acpi_cpu_tag
> > For me, if the PPTT has valid ID, we should use that. Just becuase DT lacks
> > it and uses counter doesn't mean ACPI also needs to follow that.
>
> AFAIK, a valid ACPI UID doesn't need to be something derivable directly
> from the hardware, so it's just as arbitrary as the CPU phandle that is
> in the DT cpu-map, i.e. DT *does* have an analogous leaf node integer.
>
> >
> > I am sure some vendor will put valid UID and expect that to be in the
> > sysfs.
>
> I can't think of any reason that would be useful, especially when the
> UID is for a thread, which isn't even displayed by sysfs.
>
> >
> > > (and as a side, I actually like the PE has a acpi id behavior, but for
> > > threads its being lost with this patch...)
> > >
> > > Given i've seen odd package/core ids on x86s a few years ago, it never
>
> So this inspired me to grep some x86 topology code. I found
> arch/x86/kernel/smpboot.c:topology_update_package_map(), which uses
> a counter to set the logical package id and Documentation/x86/topology.txt
> states
>
> """
> - cpuinfo_x86.logical_id:
>
> The logical ID of the package. As we do not trust BIOSes to enumerate the
> packages in a consistent way, we introduced the concept of logical package
> ID so we can sanely calculate the number of maximum possible packages in
> the system and have the packages enumerated linearly.
> """
Eh, x86 does seem to display the physical, rather than logical (linear)
IDs in sysfs though,
arch/x86/include/asm/topology.h:#define topology_physical_package_id(cpu) (cpu_data(cpu).phys_proc_id)
"""
- cpuinfo_x86.phys_proc_id:
The physical ID of the package. This information is retrieved via CPUID
and deduced from the APIC IDs of the cores in the package.
"""
So, hmmm...
But, I think we should either be looking for a hardware derived ID to use
(like x86), or remap to counters. I don't believe the current scheme of
using ACPI offsets can be better than counters, and it has consistency and
human readability issues.
Thanks,
drew
>
> Which I see as x86 precedent for the consistency argument I made in my
> other reply.
>
> Thanks,
> drew
next prev parent reply other threads:[~2018-06-29 11:55 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-28 14:51 [PATCH] arm64: acpi: reenumerate topology ids Andrew Jones
2018-06-28 16:30 ` Sudeep Holla
2018-06-28 17:12 ` Jeremy Linton
2018-06-29 10:53 ` Sudeep Holla
2018-06-29 11:42 ` Andrew Jones
2018-06-29 11:55 ` Andrew Jones [this message]
2018-06-29 13:48 ` Sudeep Holla
2018-06-29 13:38 ` Sudeep Holla
2018-06-29 16:03 ` Andrew Jones
2018-06-28 17:32 ` Andrew Jones
2018-06-29 10:29 ` Sudeep Holla
2018-06-29 11:23 ` Andrew Jones
2018-06-29 13:29 ` Sudeep Holla
2018-06-29 15:46 ` Andrew Jones
2018-06-29 15:55 ` Sudeep Holla
2018-06-29 16:48 ` Jeremy Linton
2018-06-29 17:03 ` Andrew Jones
2018-06-29 17:23 ` Sudeep Holla
2018-06-29 18:03 ` Andrew Jones
2018-07-02 14:58 ` Jeffrey Hugo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180629115539.w7lgjy2bmucgz7gm@kamzik.brq.redhat.com \
--to=drjones@redhat.com \
--cc=ard.biesheuvel@linaro.org \
--cc=catalin.marinas@arm.com \
--cc=jeremy.linton@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=shunyong.yang@hxt-semitech.com \
--cc=sudeep.holla@arm.com \
--cc=will.deacon@arm.com \
--cc=yu.zheng@hxt-semitech.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).