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Date: Wed, 11 Apr 2018 09:02:41 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Cc: cygwin-apps AT cygwin DOT com
Subject: Re: /proc/cpuinfo vs. processor groups
Message-ID: <20180411070241.GJ29703@calimero.vinschen.de>
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References: <878t9vt3vs DOT fsf AT Rainer DOT invalid>
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THanks for the report but this belongs to the cygwin ML.
I'm redirecting this here.


Corinna

On Apr 10 18:36, Achim Gratz wrote:
>=20
> As briefly discussed on IRC I've got a new Server 2016 blade with 2
> sockets =C3=97 8 cores =C3=97 2 HT =3D32 logical processors and Cygwin sp=
ews errors
> for processor ID 16 and up (also top doesn't quite work, which likely
> has the same reason, although the code path may be unrelated to the
> /proc/cpuinfo bug described here).
>=20
> --8<---------------cut here---------------start------------->8---
> 64bit (166)~ > cat /proc/cpuinfo
>       0 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(1000=
0,0 (10/16)) failed Win32 error 87
>     209 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(2000=
0,0 (11/17)) failed Win32 error 87
>     913 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(4000=
0,0 (12/18)) failed Win32 error 87
>    1047 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(8000=
0,0 (13/19)) failed Win32 error 87
>    1151 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(1000=
00,0 (14/20)) failed Win32 error 87
>    1266 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(2000=
00,0 (15/21)) failed Win32 error 87
>    1383 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(4000=
00,0 (16/22)) failed Win32 error 87
>    1479 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(8000=
00,0 (17/23)) failed Win32 error 87
>    1573 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(1000=
000,0 (18/24)) failed Win32 error 87
>    1675 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(2000=
000,0 (19/25)) failed Win32 error 87
>    1806 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(4000=
000,0 (1A/26)) failed Win32 error 87
>    1888 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(8000=
000,0 (1B/27)) failed Win32 error 87
>    1971 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(1000=
0000,0 (1C/28)) failed Win32 error 87
>    2069 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(2000=
0000,0 (1D/29)) failed Win32 error 87
>    2154 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(4000=
0000,0 (1E/30)) failed Win32 error 87
>    2247 [main] cat 10068 format_proc_cpuinfo: SetThreadGroupAffinity(8000=
0000,0 (1F/31)) failed Win32 error 87
> --8<---------------cut here---------------end--------------->8---
>=20
> It turns out this is related to processor groups and some changes that
> probably weren't even in the making when the Cygwin code was written.
> These changes were opt-in patches until 2008R2, but are now the default
> in 2016:
>=20
> https://blogs.msdn.microsoft.com/saponsqlserver/2011/10/08/uneven-windows=
-processor-groups/
>=20
> The BIOS on that server does something rather peculiar (it does make
> sense in a way, but Cygwin clearly didn't expect it):
>=20
> https://support.hpe.com/hpsc/doc/public/display?sp4ts.oid=3D7271227&docId=
=3Demr_na-c04650594&docLocale=3Den_US
>=20
> This results in Windows coming up with two 64 core processor groups that
> have 16 active logical processors each:
>=20
> --8<---------------cut here---------------start------------->8---
> (gdb) print plpi
> $1 =3D (PSYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX) 0x600008020
> (gdb) print *plpi
> $2 =3D {Relationship =3D RelationGroup, Size =3D 128, {Processor =3D {Fla=
gs =3D 2 '\002', Reserved =3D "\000\002", '\000' <repeats 18 times>, GroupC=
ount =3D 0,
>       GroupMask =3D {{Mask =3D 4160, Group =3D 0, Reserved =3D {0, 0, 0}}=
}}, NumaNode =3D {NodeNumber =3D 131074, Reserved =3D '\000' <repeats 19 ti=
mes>,
>       GroupMask =3D {Mask =3D 4160, Group =3D 0, Reserved =3D {0, 0, 0}}}=
, Cache =3D {Level =3D 2 '\002', Associativity =3D 0 '\000', LineSize =3D 2=
, CacheSize =3D 0,
>       Type =3D CacheUnified, Reserved =3D '\000' <repeats 12 times>, "@\0=
20\000\000\000\000\000", GroupMask =3D {Mask =3D 0, Group =3D 0, Reserved =
=3D {0, 0,
>           0}}}, Group =3D {MaximumGroupCount =3D 2, ActiveGroupCount =3D =
2, Reserved =3D '\000' <repeats 19 times>, GroupInfo =3D {{
>           MaximumProcessorCount =3D 64 '@', ActiveProcessorCount =3D 16 '=
\020', Reserved =3D '\000' <repeats 37 times>, ActiveProcessorMask =3D 6553=
5}}}}}
> --8<---------------cut here---------------end--------------->8---
>=20
> I've confirmed that the error message is not printed if I manually
> correct the information for processor ID 17 as follows:
>=20
> --8<---------------cut here---------------start------------->8---
> (gdb) print affinity=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20
> $2 =3D {Mask =3D 131072, Group =3D 0, Reserved =3D {0, 0, 0}}=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
> (gdb) set affinity.Mask=3D2=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20
> (gdb) set affinity.Group=3D1
> --8<---------------cut here---------------end--------------->8---
>=20
> However, the same or possibly even stranger processor group setups can
> be created using boot options that force different organizations of
> processor groups.  There is an option to force a seperate processor
> group for each NUMA node and another one to force a specific number of
> groups.  The upshot is that even the first processor groups may not have
> the maximum number of processors present, so you need to check the
> number of active processors instead.  I couldn't find out if the
> processor mask is still guaranteed to be filled from the LSB contigously
> or whether one can rely on only the last group to have less than the
> first few.  It seems more prudent to check the group specific
> ActiveProcessorMask, although that significantly complicates the code.
> I don't think Windows can currently switch CPU online/offline when
> booted.
>=20
>=20
> As an aside, the cache size is reported as 256kiB (not just for this
> processor, but also for a Celeron 1037U on another machine), which seems
> to be the L2 cache for a single hardware core on these architectures.
> Linux now reports L3 cache sizes (and possibly L4 if present) for these
> (20MiB and 2MiB per socket respectively).
>=20
>=20
> Regards,
> Achim.
> --
> +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
>=20
> Factory and User Sound Singles for Waldorf Blofeld:
> http://Synth.Stromeko.net/Downloads.html#WaldorfSounds

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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