On 13.03.21 14:48, Mike Rapoport wrote:
Hi,
On Sat, Mar 13, 2021 at 10:05:23AM +0100, David Hildenbrand wrote:
Am 13.03.2021 um 05:04 schrieb Liang, Liang (Leo) <Liang.Liang@xxxxxxx>:
Hi David,
Which benchmark tool you prefer? Memtest86+ or else?
Hi Leo,
I think you want something that runs under Linux natively.
I‘m planning on coding up a kernel module to walk all 4MB pages in the
freelists and perform a stream benchmark individually. Then we might be
able to identify the problematic range - if there is a problematic range :)
My wild guess would be that the pages that are now at the head of free
lists have wrong caching enabled. Might be worth checking in your test
module.
I hacked something up real quick:
https://github.com/davidhildenbrand/kstream
Only briefly tested inside a VM. The output looks something like
[...]
[ 8396.432225] [0x0000000045800000 - 0x0000000045bfffff] 25322 MB/s /
38948 MB/s
[ 8396.448749] [0x0000000045c00000 - 0x0000000045ffffff] 24481 MB/s /
38946 MB/s
[ 8396.465197] [0x0000000046000000 - 0x00000000463fffff] 24892 MB/s /
39170 MB/s
[ 8396.481552] [0x0000000046400000 - 0x00000000467fffff] 25222 MB/s /
39156 MB/s
[ 8396.498012] [0x0000000046800000 - 0x0000000046bfffff] 24416 MB/s /
39159 MB/s
[ 8396.514397] [0x0000000046c00000 - 0x0000000046ffffff] 25469 MB/s /
38940 MB/s
[ 8396.530849] [0x0000000047000000 - 0x00000000473fffff] 24885 MB/s /
38734 MB/s
[ 8396.547195] [0x0000000047400000 - 0x00000000477fffff] 25458 MB/s /
38941 MB/s
[...]
The benchmark allocates one 4 MiB chunk at a time and runs a simplified
STREAM benchmark a) without flushing caches b) flushing caches before
every memory access.
It would be great if you could run that with the *old behavior* kernel
(IOW, without 7fef431be9c9), so we might still be lucky to catch the
problematic area in the freelist.
Let's see if that will indicate anything.
--
Thanks,
David / dhildenb
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