#16622: kernel: system_info.used_pages don't include mapped files
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Reporter: X512 | Owner: nobody
Type: bug | Status: new
Priority: normal | Milestone: Unscheduled
Component: System/Kernel | Version: R1/Development
Resolution: | Keywords:
Blocked By: | Blocking:
Platform: All |
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Description changed by X512:
Old description:
This is hrev54741.
As discussed [https://discuss.haiku-os.org/t/app-server-font-cache-is-
causing-high-cpu-load-in-low-resource-manager-thread-and-cause-
mysterious-resource-exhaustment/10147/13 here], mapping files to read-
only areas almost not affect `system_info.used_pages` that is used by
most memory inspecting utilities, but it actually consumes memory and
make allocations not possible if too many files are mapped.
`system_info.needed_memory` provides correct information about free
memory but is also seems to include disk cache that can be freed to
release memory for allocations.
If memory mapped files are consuming memory, they should be included in
`system_info.used_pages`.
Actually it is not required to reserve memory for read-only mapped files
because it can be handled in similar way as disk cache: load file
contents on demand and unload when memory is needed by someone else. This
approach do not violate no overcommit policy. If program change area
protection and enable copy-on-write, attempt may failed with out of
memory if memory can't be reserved.
