Re: [PATCH] [Request for inclusion] Filesystem in Userspace

[Miklos Szeredi]

> Measured under what conditions?

  dorka:/home/miko/fuse-bugfix# touch /tmp/fusenull
  dorka:/home/miko/fuse-bugfix# example/null  /tmp/fusenull
  dorka:/home/miko/fuse-bugfix# time dd if=/dev/zero of=/tmp/fusenull bs=4096 count=262144
  262144+0 records in
  262144+0 records out
  1073741824 bytes transferred in 12.591578 seconds (85274604 bytes/sec)
  
  real    0m12.662s
  user    0m0.189s
  sys     0m8.156s
  dorka:/home/miko/fuse-bugfix# fusermount -u /tmp/fusenull

fusenull is a /dev/null like filesystem implemented with the libfuse
API (see fuse sources).

> There may be only one dirty page in the whole system and it may be the
> one backed by FUSE. Now yes, if it was not backed by FUSE, I would be in
> trouble -- but the OOM killer would get me out. It will *NOT* get me out
> with fuse, because it thinks the page will be cleaned, which it won't.

OK, I see your point.  But can't the memory subsystem be tought, that
those pages are not guaranteed to be written back in a limited time?

Miklos
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