[AMD Public Use]
Hi David and Mike,
It's BIOS buggy. Now fixed by new BIOS. Thanks you so much! Cheers!
[ 0.000034] MTRR variable ranges enabled:
[ 0.000035] 0 base 000000000000 mask FFFF80000000 write-back
[ 0.000037] 1 base 0000FFE00000 mask FFFFFFE00000 write-protect
[ 0.000039] 2 base 0000FFDE0000 mask FFFFFFFE0000 write-protect
[ 0.000040] 3 base 0000FF000000 mask FFFFFFF80000 write-protect
[ 0.000041] 4 disabled
[ 0.000042] 5 disabled
[ 0.000043] 6 disabled
[ 0.000044] 7 disabled
[ 0.000045] TOM2: 0000000280000000 aka 10240M
root@scbu-Chachani:/home/scbu# cat /proc/mtrr
reg00: base=0x000000000 ( 0MB), size= 2048MB, count=1: write-back
reg01: base=0x0ffe00000 ( 4094MB), size= 2MB, count=1: write-protect
reg02: base=0x0ffde0000 ( 4093MB), size= 128KB, count=1: write-protect
reg03: base=0x0ff000000 ( 4080MB), size= 512KB, count=1: write-protect
BRs,
Leo
-----Original Message-----
From: Mike Rapoport <r...@linux.ibm.com>
Sent: Tuesday, March 16, 2021 6:30 PM
To: David Hildenbrand <da...@redhat.com>
Cc: Liang, Liang (Leo) <liang.li...@amd.com>; Deucher, Alexander
<alexander.deuc...@amd.com>; linux-ker...@vger.kernel.org; amd-gfx list
<amd-gfx@lists.freedesktop.org>; Andrew Morton <a...@linux-foundation.org>;
Huang, Ray <ray.hu...@amd.com>; Koenig, Christian <christian.koe...@amd.com>;
Rafael J. Wysocki <raf...@kernel.org>; George Kennedy
<george.kenn...@oracle.com>
Subject: Re: slow boot with 7fef431be9c9 ("mm/page_alloc: place pages to tail
in __free_pages_core()")
On Tue, Mar 16, 2021 at 10:08:10AM +0100, David Hildenbrand wrote:
> On 16.03.21 09:58, Liang, Liang (Leo) wrote:
> > [AMD Public Use]
> >
> > Hi David,
> >
> > root@scbu-Chachani:~# cat /proc/mtrr
> > reg00: base=0x000000000 ( 0MB), size= 2048MB, count=1: write-back
> > reg01: base=0x0ffe00000 ( 4094MB), size= 2MB, count=1: write-protect
> > reg02: base=0x100000000 ( 4096MB), size= 16MB, count=1: write-protect
>
> ^ there it is
>
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwiki
> .osdev.org%2FMTRR&data=04%7C01%7CLiang.Liang%40amd.com%7C49c791cc6
> 18745b8c35208d8e86679a1%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C6
> 37514874126576401%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoi
> V2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=667IK3Bnyx5uP3
> rKN8bOjW7A2MBuM1sLCg98m1LCIGo%3D&reserved=0
>
> "Reads allocate cache lines on a cache miss. All writes update main memory.
>
> Cache lines are not allocated on a write miss. Write hits invalidate
> the cache line and update main memory. "
>
> AFAIU, writes completely bypass caches and store directly to main
> mamory. If there are cache lines from a previous read, they are
> invalidated. So I think especially slow will be read(addr),
> write(addr), read(addr), ... which is what we have in the kstream benchmark.
>
>
> The question is:
>
> who sets this up without owning the memory?
> Is the memory actually special/slow or is that setting wrong?
I really doubt that 16M at 0x100000000 in a system with 8G RAM would
*physically* differ from the neighbouring memory.
> Buggy firmware/BIOS?
> Buggy device driver?
[ 0.000027] MTRR default type: uncachable
[ 0.000028] MTRR fixed ranges enabled:
[ 0.000030] 00000-9FFFF write-back
[ 0.000031] A0000-BFFFF uncachable
[ 0.000032] C0000-FFFFF write-through
[ 0.000033] MTRR variable ranges enabled:
[ 0.000034] 0 base 000000000000 mask FFFF80000000 write-back
[ 0.000036] 1 base 0000FFE00000 mask FFFFFFE00000 write-protect
[ 0.000037] 2 base 000100000000 mask FFFFFF000000 write-protect
As we have the range at 0x100000000 write-protected reported that early in boot
I'd say it's BIOS.
The question is how to reliably detect that this is a bogus setting...
[ 0.000038] 3 base 0000FFDE0000 mask FFFFFFFE0000 write-protect
[ 0.000039] 4 base 0000FF000000 mask FFFFFFF80000 write-protect
[ 0.000040] 5 disabled
[ 0.000041] 6 disabled
[ 0.000042] 7 disabled
[ 0.000042] TOM2: 0000000280000000 aka 10240M
--
Sincerely yours,
Mike.
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