mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-15 16:24:13 +08:00
6614a3c316
Lin, Yang Shi, Anshuman Khandual and Mike Rapoport
- Some kmemleak fixes from Patrick Wang and Waiman Long
- DAMON updates from SeongJae Park
- memcg debug/visibility work from Roman Gushchin
- vmalloc speedup from Uladzislau Rezki
- more folio conversion work from Matthew Wilcox
- enhancements for coherent device memory mapping from Alex Sierra
- addition of shared pages tracking and CoW support for fsdax, from
Shiyang Ruan
- hugetlb optimizations from Mike Kravetz
- Mel Gorman has contributed some pagealloc changes to improve latency
and realtime behaviour.
- mprotect soft-dirty checking has been improved by Peter Xu
- Many other singleton patches all over the place
-----BEGIN PGP SIGNATURE-----
iHUEABYKAB0WIQTTMBEPP41GrTpTJgfdBJ7gKXxAjgUCYuravgAKCRDdBJ7gKXxA
jpqSAQDrXSdII+ht9kSHlaCVYjqRFQz/rRvURQrWQV74f6aeiAD+NHHeDPwZn11/
SPktqEUrF1pxnGQxqLh1kUFUhsVZQgE=
=w/UH
-----END PGP SIGNATURE-----
Merge tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
"Most of the MM queue. A few things are still pending.
Liam's maple tree rework didn't make it. This has resulted in a few
other minor patch series being held over for next time.
Multi-gen LRU still isn't merged as we were waiting for mapletree to
stabilize. The current plan is to merge MGLRU into -mm soon and to
later reintroduce mapletree, with a view to hopefully getting both
into 6.1-rc1.
Summary:
- The usual batches of cleanups from Baoquan He, Muchun Song, Miaohe
Lin, Yang Shi, Anshuman Khandual and Mike Rapoport
- Some kmemleak fixes from Patrick Wang and Waiman Long
- DAMON updates from SeongJae Park
- memcg debug/visibility work from Roman Gushchin
- vmalloc speedup from Uladzislau Rezki
- more folio conversion work from Matthew Wilcox
- enhancements for coherent device memory mapping from Alex Sierra
- addition of shared pages tracking and CoW support for fsdax, from
Shiyang Ruan
- hugetlb optimizations from Mike Kravetz
- Mel Gorman has contributed some pagealloc changes to improve
latency and realtime behaviour.
- mprotect soft-dirty checking has been improved by Peter Xu
- Many other singleton patches all over the place"
[ XFS merge from hell as per Darrick Wong in
https://lore.kernel.org/all/YshKnxb4VwXycPO8@magnolia/ ]
* tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (282 commits)
tools/testing/selftests/vm/hmm-tests.c: fix build
mm: Kconfig: fix typo
mm: memory-failure: convert to pr_fmt()
mm: use is_zone_movable_page() helper
hugetlbfs: fix inaccurate comment in hugetlbfs_statfs()
hugetlbfs: cleanup some comments in inode.c
hugetlbfs: remove unneeded header file
hugetlbfs: remove unneeded hugetlbfs_ops forward declaration
hugetlbfs: use helper macro SZ_1{K,M}
mm: cleanup is_highmem()
mm/hmm: add a test for cross device private faults
selftests: add soft-dirty into run_vmtests.sh
selftests: soft-dirty: add test for mprotect
mm/mprotect: fix soft-dirty check in can_change_pte_writable()
mm: memcontrol: fix potential oom_lock recursion deadlock
mm/gup.c: fix formatting in check_and_migrate_movable_page()
xfs: fail dax mount if reflink is enabled on a partition
mm/memcontrol.c: remove the redundant updating of stats_flush_threshold
userfaultfd: don't fail on unrecognized features
hugetlb_cgroup: fix wrong hugetlb cgroup numa stat
...
87 lines
2.6 KiB
ReStructuredText
87 lines
2.6 KiB
ReStructuredText
=====================
|
|
Overcommit Accounting
|
|
=====================
|
|
|
|
The Linux kernel supports the following overcommit handling modes
|
|
|
|
0
|
|
Heuristic overcommit handling. Obvious overcommits of address
|
|
space are refused. Used for a typical system. It ensures a
|
|
seriously wild allocation fails while allowing overcommit to
|
|
reduce swap usage. root is allowed to allocate slightly more
|
|
memory in this mode. This is the default.
|
|
|
|
1
|
|
Always overcommit. Appropriate for some scientific
|
|
applications. Classic example is code using sparse arrays and
|
|
just relying on the virtual memory consisting almost entirely
|
|
of zero pages.
|
|
|
|
2
|
|
Don't overcommit. The total address space commit for the
|
|
system is not permitted to exceed swap + a configurable amount
|
|
(default is 50%) of physical RAM. Depending on the amount you
|
|
use, in most situations this means a process will not be
|
|
killed while accessing pages but will receive errors on memory
|
|
allocation as appropriate.
|
|
|
|
Useful for applications that want to guarantee their memory
|
|
allocations will be available in the future without having to
|
|
initialize every page.
|
|
|
|
The overcommit policy is set via the sysctl ``vm.overcommit_memory``.
|
|
|
|
The overcommit amount can be set via ``vm.overcommit_ratio`` (percentage)
|
|
or ``vm.overcommit_kbytes`` (absolute value). These only have an effect
|
|
when ``vm.overcommit_memory`` is set to 2.
|
|
|
|
The current overcommit limit and amount committed are viewable in
|
|
``/proc/meminfo`` as CommitLimit and Committed_AS respectively.
|
|
|
|
Gotchas
|
|
=======
|
|
|
|
The C language stack growth does an implicit mremap. If you want absolute
|
|
guarantees and run close to the edge you MUST mmap your stack for the
|
|
largest size you think you will need. For typical stack usage this does
|
|
not matter much but it's a corner case if you really really care
|
|
|
|
In mode 2 the MAP_NORESERVE flag is ignored.
|
|
|
|
|
|
How It Works
|
|
============
|
|
|
|
The overcommit is based on the following rules
|
|
|
|
For a file backed map
|
|
| SHARED or READ-only - 0 cost (the file is the map not swap)
|
|
| PRIVATE WRITABLE - size of mapping per instance
|
|
|
|
For an anonymous or ``/dev/zero`` map
|
|
| SHARED - size of mapping
|
|
| PRIVATE READ-only - 0 cost (but of little use)
|
|
| PRIVATE WRITABLE - size of mapping per instance
|
|
|
|
Additional accounting
|
|
| Pages made writable copies by mmap
|
|
| shmfs memory drawn from the same pool
|
|
|
|
Status
|
|
======
|
|
|
|
* We account mmap memory mappings
|
|
* We account mprotect changes in commit
|
|
* We account mremap changes in size
|
|
* We account brk
|
|
* We account munmap
|
|
* We report the commit status in /proc
|
|
* Account and check on fork
|
|
* Review stack handling/building on exec
|
|
* SHMfs accounting
|
|
* Implement actual limit enforcement
|
|
|
|
To Do
|
|
=====
|
|
* Account ptrace pages (this is hard)
|