diff options
| author | Rodrigo Vivi <[email protected]> | 2018-07-23 09:13:12 -0700 |
|---|---|---|
| committer | Rodrigo Vivi <[email protected]> | 2018-07-23 09:13:12 -0700 |
| commit | c74a7469f97c0f40b46e82ee979f9fb1bb6e847c (patch) | |
| tree | f2690a1a916b73ef94657fbf0e0141ae57701825 /Documentation/vm/remap_file_pages.txt | |
| parent | 6f15a7de86c8cf2dc09fc9e6d07047efa40ef809 (diff) | |
| parent | 500775074f88d9cf5416bed2ca19592812d62c41 (diff) | |
Merge drm/drm-next into drm-intel-next-queued
We need a backmerge to get DP_DPCD_REV_14 before we push other
i915 changes to dinq that could break compilation.
Signed-off-by: Rodrigo Vivi <[email protected]>
Diffstat (limited to 'Documentation/vm/remap_file_pages.txt')
| -rw-r--r-- | Documentation/vm/remap_file_pages.txt | 27 |
1 files changed, 0 insertions, 27 deletions
diff --git a/Documentation/vm/remap_file_pages.txt b/Documentation/vm/remap_file_pages.txt deleted file mode 100644 index f609142f406a..000000000000 --- a/Documentation/vm/remap_file_pages.txt +++ /dev/null @@ -1,27 +0,0 @@ -The remap_file_pages() system call is used to create a nonlinear mapping, -that is, a mapping in which the pages of the file are mapped into a -nonsequential order in memory. The advantage of using remap_file_pages() -over using repeated calls to mmap(2) is that the former approach does not -require the kernel to create additional VMA (Virtual Memory Area) data -structures. - -Supporting of nonlinear mapping requires significant amount of non-trivial -code in kernel virtual memory subsystem including hot paths. Also to get -nonlinear mapping work kernel need a way to distinguish normal page table -entries from entries with file offset (pte_file). Kernel reserves flag in -PTE for this purpose. PTE flags are scarce resource especially on some CPU -architectures. It would be nice to free up the flag for other usage. - -Fortunately, there are not many users of remap_file_pages() in the wild. -It's only known that one enterprise RDBMS implementation uses the syscall -on 32-bit systems to map files bigger than can linearly fit into 32-bit -virtual address space. This use-case is not critical anymore since 64-bit -systems are widely available. - -The syscall is deprecated and replaced it with an emulation now. The -emulation creates new VMAs instead of nonlinear mappings. It's going to -work slower for rare users of remap_file_pages() but ABI is preserved. - -One side effect of emulation (apart from performance) is that user can hit -vm.max_map_count limit more easily due to additional VMAs. See comment for -DEFAULT_MAX_MAP_COUNT for more details on the limit. |