Messages in this thread | | | From | Linus Torvalds <> | Date | Sat, 30 Nov 2019 14:35:06 -0800 | Subject | Re: [x86/mm/pat] 8d04a5f97a: phoronix-test-suite.glmark2.0.score -23.7% regression |
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On Sat, Nov 30, 2019 at 2:09 PM Mariusz Ceier <mceier@gmail.com> wrote: > > Contents of /sys/kernel/debug/x86/pat_memtype_list on master > (32ef9553635ab1236c33951a8bd9b5af1c3b1646) where performance is > degraded:
Diff between good and bad case:
@@ -1,8 +1,8 @@ PAT memtype list: write-back @ 0x55ba4000-0x55ba5000 write-back @ 0x5e88c000-0x5e8b5000 -write-back @ 0x5e8b4000-0x5e8b8000 write-back @ 0x5e8b4000-0x5e8b5000 +write-back @ 0x5e8b4000-0x5e8b8000 write-back @ 0x5e8b7000-0x5e8bb000 write-back @ 0x5e8ba000-0x5e8bc000 write-back @ 0x5e8bb000-0x5e8be000 @@ -21,15 +21,15 @@ uncached-minus @ 0xec260000-0xec264000 uncached-minus @ 0xec300000-0xec320000 uncached-minus @ 0xec326000-0xec327000 -uncached-minus @ 0xf0000000-0xf0001000 uncached-minus @ 0xf0000000-0xf8000000 +uncached-minus @ 0xf0000000-0xf0001000 uncached-minus @ 0xfdc43000-0xfdc44000 uncached-minus @ 0xfe000000-0xfe001000 uncached-minus @ 0xfed00000-0xfed01000 uncached-minus @ 0xfed10000-0xfed16000 uncached-minus @ 0xfed90000-0xfed91000 -write-combining @ 0x2000000000-0x2100000000 -write-combining @ 0x2000000000-0x2100000000 +uncached-minus @ 0x2000000000-0x2100000000 +uncached-minus @ 0x2000000000-0x2100000000 uncached-minus @ 0x2100000000-0x2100001000 uncached-minus @ 0x2100001000-0x2100002000 uncached-minus @ 0x2ffff10000-0x2ffff20000
the first two differences are just trivial ordering differences for overlapping ranges (starting at 0x5e8b4000 and 0xf0000000) respectively.
But the final difference is a real difference where it used to be WC, and is now UC-:
-write-combining @ 0x2000000000-0x2100000000 -write-combining @ 0x2000000000-0x2100000000 +uncached-minus @ 0x2000000000-0x2100000000 +uncached-minus @ 0x2000000000-0x2100000000
which certainly could easily explain the huge performance degradation.
Linus
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