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Line 30:
Line 30: − + + + + + + + + + + + + + + + + + + + − The 2nd longest routine. It takes ~ 0.07 seconds on dump. + − + + + + − === Fork vs VMA restore ===+ − We restore task's mappings before it goes forking to handle COW. This effectively serializes forking.+ +
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11 openat(AT_FDCWD, "/proc/$pid/map_files", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 4
11 openat(AT_FDCWD, "/proc/$pid/map_files", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 4
=== <code>parasite_fuxup_vdso</code> ===
== Restore ==
=== Fork vs VMA restore ===
We restore task's mappings before it goes forking to handle COW. This effectively serializes forking.
=== Restoring VMAs ===
There are 4 stages in VMA restore. Relative times of each are below
* Reading images 1%
* Mapping huuge premap area << 1%
* (Re-)mapping sub-areas 73%
* Filling area with data 26%
The 3rd stage has two parts. With timings:
* Opening filemap fd 85%
* Maping vma 15%
=== Opening files for mappings ===
== Restore ==
The <code>get_filemap_fd()</code> opens new fd every time. If a file is mapped several
times (e.g. -- a library) we can share one fd for that.
=== Staging ===
When restoring a single task CRIU uses [[stages of restoring]] which slows things down. Need either special-care the single task restore, or introduce fine-grained locking for such things.
[[Category: Development]]
[[Category: Thinkers]]