[sheepdog-users] Allowed open files question

[Andrew J. Hobbs]

When I start sheepdog, I'm continuing to get a message suggesting 
6144000 files for nofiles.  Which is evidently from sheep.c where it's 
defined as:
#define SD_RLIM_NOFILE (SD_MAX_NODES * 100 * 10)

Excepting, what I'm finding is attempting to set anywhere near this 
limit I'm getting bounced down to 1024.  However, it seems 
include/linux/fs.h fixes an absolute upper limit on fd numbers of 
1024*1024 or 1048576, which seems to bear out.  Using ulimit -SHn 
1048576 works fine, 1048577 errors with the following:
-bash: ulimit: open files: cannot modify limit: Operation not permitted

Altering fs.file-max to a larger value does not affect the ulimit 
ability at all, although the system will show that it's been set to this 
upper value.

Going off of the calculation for SD_RLIM_NOFILE, that hardcoded linux 
kernel value would allow up to 1048 nodes while still being under the 
cap.  Perhaps a message to that effect would be in order? I've spent a 
fair amount of time trying to make that message go away before figuring 
this out.  I've not looked into whether there are any adverse effects of 
altering the maximum through fs.h and recompiling, but that's not really 
something I'm interested in doing.

A note indicating set nofile to 1048576, or up to 6144000 if number of 
nodes > 1048, perhaps?

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