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

Miklos Szeredi
2004-11-21T11:29:52Z

> 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