Bug#827322: multipath-tools: Not all paths discovered when large number of paths are present

[Ritesh Raj Sarraf]

Control: tag -1 moreinfo

On Tue, 2016-06-14 at 17:30 -0600, Andrew Patterson wrote:
> There is no output in dmesg.
> 
> Changing /proc/sys/fs/aio-max-nr from the default 65536 to 1048576
> seems to help. With this change, I can go up to 256 LUNs (1024 paths)
> with no problems.
> 
> I have seen similar issues in earlier versions of multipath-tools.

Thank you for bringing this up, and the pointer. In multipath.conf there was a
directive added for something similar.


       max_fds          Specify  the  maximum  number of file descriptors that
                        can be opened by multipath and  multipathd.   This  is
                        equivalent  to ulimit -n. A value of max will set this
                        to the system limit from /proc/sys/fs/nr_open. If this
                        is  not  set,  the maximum number of open fds is taken
                        from the calling process. It is usually  1024.  To  be
                        safe,  this  should  be  set  to the maximum number of
                        paths plus 32, if that number is greated than 1024.


It seems to be inline with what aio-max-nr documentation says.

==============================================================

aio-nr & aio-max-nr:

aio-nr is the running total of the number of events specified on the
io_setup system call for all currently active aio contexts.  If aio-nr
reaches aio-max-nr then io_setup will fail with EAGAIN.  Note that
raising aio-max-nr does not result in the pre-allocation or re-sizing
of any kernel data structures.

==============================================================


Have you tried it with the "max_fds" option set ?


-- 
Ritesh Raj Sarraf | http://people.debian.org/~rrs
Debian - The Universal Operating System
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