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Diffstat (limited to 'Documentation/vm/soft-dirty.txt')
| -rw-r--r-- | Documentation/vm/soft-dirty.txt | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/vm/soft-dirty.txt b/Documentation/vm/soft-dirty.txt index 9a12a5956bc..55684d11a1e 100644 --- a/Documentation/vm/soft-dirty.txt +++ b/Documentation/vm/soft-dirty.txt @@ -28,6 +28,13 @@ This is so, since the pages are still mapped to physical memory, and thus all the kernel does is finds this fact out and puts both writable and soft-dirty bits on the PTE. + While in most cases tracking memory changes by #PF-s is more than enough +there is still a scenario when we can lose soft dirty bits -- a task +unmaps a previously mapped memory region and then maps a new one at exactly +the same place. When unmap is called, the kernel internally clears PTE values +including soft dirty bits. To notify user space application about such +memory region renewal the kernel always marks new memory regions (and +expanded regions) as soft dirty. This feature is actively used by the checkpoint-restore project. You can find more details about it on http://criu.org |