Public bug reported:
This is a public version of https://bugs.launchpad.net/bugs/2034985
Backport: 6852c46c783d mm/mmap: move vma operations to mm_struct out of
the critical section of file mapping lock (merged upstream in 6.6) to
jammy
[Impact]
The msg_bytes and msg_hdrs atomic counters are frequently updated when IPC msg
queue is in heavy use, causing heavy cache bounce and overhead. Change them to
percpu_counter greatly improve the performance. Since there is one percpu
struct per namespace, additional memory cost is minimal. Reading of the count
done in msgctl call, which is infrequent. So the need to sum up the counts in
each CPU is infrequent.
[Fix]
Backport:
6852c46c783d mm/mmap: move vma operations to mm_struct out of the critical
section of file mapping lock
[Test]
I have tested this code.
[Where problems could occur]
TODO
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Affects: linux (Ubuntu Jammy)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu)
Importance: Undecided
Status: New
** No longer affects: intel
** Also affects: linux (Ubuntu Jammy)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2058488
Title:
[SPR] performance: Remove operations to mm_struct out of file mapping
lock's critical section
Status in linux package in Ubuntu:
New
Status in linux source package in Jammy:
New
Bug description:
This is a public version of https://bugs.launchpad.net/bugs/2034985
Backport: 6852c46c783d mm/mmap: move vma operations to mm_struct out
of the critical section of file mapping lock (merged upstream in 6.6)
to jammy
[Impact]
The msg_bytes and msg_hdrs atomic counters are frequently updated when IPC
msg queue is in heavy use, causing heavy cache bounce and overhead. Change them
to percpu_counter greatly improve the performance. Since there is one percpu
struct per namespace, additional memory cost is minimal. Reading of the count
done in msgctl call, which is infrequent. So the need to sum up the counts in
each CPU is infrequent.
[Fix]
Backport:
6852c46c783d mm/mmap: move vma operations to mm_struct out of the critical
section of file mapping lock
[Test]
I have tested this code.
[Where problems could occur]
TODO
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