Re: [fuse-devel] [PATCH] mm: strictlimit feature -v4

[Maxim P. <MPa...@pa...>]

Hi Fengguang,

>> I'd like to test the patches out and take a look at its runtime
>> behaviors. I've managed to setup general dd writeback tests. Do you
>> happen to have some scripts that can specifically test out the fuse
>> cases?
>
>I used ordinary dd over fuse mount for testing. But fuse setup was 
>tricky. I'll send a writeup of my test environment to you tomorrow.

The kernel part I used for testing was Linus' 3.11.0-rc6 with patchset
"fuse: An attempt to implement a write-back cache policy" v5 applied.
I understand that picking up from mailing list archives and applying
16 patches may be cumbersome, so I'll email a tar-archive with them
for your convenience.

The userspace part is a clone of
git://fuse.git.sourceforge.net/gitroot/fuse/fuse
with two patches following this email applied.

After compilation, 'fusexmp_fh' appears in 'example' subdir. fusexmp_fh
is a trivial example fuse filesystem that passes requests backend
transparently. E.g. write(2) on fuse mount leads to FUSE_WRITE request
which, in turn, is processed as write(2) on host filesystem.

I used the following variations of options on mounting fuse:

1. # fusexmp_fh -o writeback_cache /fuse
(here some amount of dirty memory on fuse bdi coexists with that on host fs)

2. # FUSE_WB=1 fusexmp_fh -o writeback_cache /fuse
(model write bandwidth equal to 1MB/s for each "data server"; here
userspace fuse is capable to process many FUSE_WRITE requests simultaneously,
so the situation with high degree of parallelism is modelled)

3. # FUSE_WB=100 fusexmp_fh -o writeback_cache /fuse
(the same as above, but bandwidth equal to 100MB/s)

4. # FUSE_WB=1 fusexmp_fh -s -o writeback_cache /fuse
(bandwidth equal to 1MB/s; userspace fuse processes all requests in
serialized manner)

5. # FUSE_WB=100 fusexmp_fh -s -o writeback_cache /fuse
(the same as above, but bandwidth equal to 100MB/s)

For each variant I ran "dd if=/dev/zero of=/fuse/foo bs=1M count=N" to
observe the behaviour of balance_dirty_pages and friends. Also, for
each variant I experimented with fuse bdi max_ratio=1% (default) and 100%
(set manually by echo 100 > /sys/devices/virtual/bdi/0:M/max_ratio).

Thanks,
Maxim

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