[SRU][jammy][PATCH 0/1] performance: mm/percpu-internal.h: Re-layout pcpu_chunk to mitigate false sharing

[Philip Cox]

BugLink: https://bugs.launchpad.net/bugs/2053152

SRU Justification:

[Impact]
Having 'base_addr' in the same cache line as 'free_bytes', 'chunk_md', and
'base_addr' causes a performance impact on x86_64 systems which can be
observed while running UnixBench/Excel throughput.

[Fix]
 In current pcpu_chunk layout, `base_addr' is in the same cache line with
`free_bytes' and `chunk_md', and `base_addr' is at the last 8 bytes.
This patch moves `bound_map' up to `base_addr', to let `base_addr' locate 
in a new cacheline.

[Test Plan]
I have tested this patch, as has Intel.  This patch has been upstreamed since 6.5 as well.

[Where problems could occur]
The risk for regression is minimal as there should be no logic change to the code, and just
a struct is being ordered differently.  This change has been upstreamed for a while with no issues.

-- 


Yu Ma (1):
  percpu-internal/pcpu_chunk: re-layout pcpu_chunk structure to reduce
    false sharing

 mm/percpu-internal.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

-- 
2.34.1