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#Notes on tmpfs

## mach-defpager

    <tschwinge>: 1. On every system there is a ``default pager'' (mach-defpager).  That one is responsible 
    for all ``anonymous memory''.  For example, when you do malloc(10 MiB), and then there is memory pressure, 
    this 10 MiB memory region is backed by the default pager, whose job then is it to provide the backing store for this.
    <tschwinge>: This is what commonly would be known as a swap partition.
    <tschwinge>: And this is also the way tmpfs works (as I understand it).
    <tschwinge>: malloc(10 MiB) can also be mmap(MAP_ANONYMOUS, 10 MIB); that's the same, essentially.
    <tschwinge>: Now, for ext2fs or any other disk-based file system, this is different:
    <tschwinge>: The ext2fs translator implements its own backing store, namely it accesses the disk for storing 
    changed file content, or to read in data from disk if a new file is opened.

## Steps

1. Find out what causes crashes in tmpfs with defpager

2. Write own pager

    6.11.11 Reading/writing for files that fit in vm_page_size works

#Debugging

To debug tmpfs, using libraries from "$PWD"/lib and trace rpc:

settrans -ca foo /usr/bin/env LD_LIBRARY_PATH="$PWD"/lib utils/rpctrace -I /usr/share/msgids/ tmpfs/tmpfs 1M