Avoid initialization of every calloc'd int in fd_map #161
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libkqueue allocates the the number of available file descriptors for the fd_map array in linux/platform.c to. That limit is vast in Docker, for complicated reasons: 1073741816 The library allocates arrays of that size in several places, but in only one does it then also _initialize_ every member of the array (to -1). Since calloc/mmap are optimized to allocate lazily, this means that only that instance winds up immediately actually using ~4GB in memory. The initialization of the int array uses -1 to indicate that a field isn't in use. The patch changes this to use 0 as unused, simply bumping the stored fds by one upon insert and decrementing by one on access, via helpers.
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libkqueue allocates the the number of available file descriptors for the fd_map array in linux/platform.c to. That limit is vast in Docker, for complicated reasons:
1073741816
The library allocates arrays of that size in several places, but in only one does it then also initialize every member of the array (to -1). Since calloc/mmap are optimized to allocate lazily, this means that only that instance winds up immediately actually using ~4GB in memory.
The initialization of the int array uses -1 to indicate that a field isn't in use. The patch changes this to use 0 as unused, simply bumping the stored fds by one upon insert and decrementing by one on access, via helpers.
Fixes #153