bionic (8) vfs_aio_pthread.8.gz

NAME

       vfs_aio_pthread - implement async I/O in Samba vfs using a pthread pool

SYNOPSIS

       vfs objects = aio_pthread

DESCRIPTION

       This VFS module is part of the samba(7) suite.

       The aio_pthread VFS module enables asynchronous I/O for Samba on platforms which have the pthreads API
       available, without using the Posix AIO interface. Posix AIO can suffer from severe limitations. For
       example, on some Linux versions the real-time signals that it uses are broken under heavy load. Other
       systems only allow AIO when special kernel modules are loaded or only allow a certain system-wide amount
       of async requests being scheduled. Systems based on glibc (most Linux systems) only allow a single
       outstanding request per file descriptor which essentially makes Posix AIO useless on systems using the
       glibc implementation.

       To work around all these limitations, the aio_pthread module was written. It uses a pthread pool instead
       of the internal Posix AIO interface to allow read and write calls to be process asynchronously. A pthread
       pool is created which expands dynamically by creating new threads as work is given to it to a maximum of
       100 threads per smbd process. To change this limit see the "aio num threads" parameter below. New threads
       are not created if idle threads are available when a new read or write request is received, the new work
       is given to an existing idle thread. Threads terminate themselves if idle for one second.

       Note that the smb.conf parameters aio read size and aio write size must also be set appropriately for
       this module to be active.

       This module MUST be listed last in any module stack as the Samba VFS pread/pwrite interface is not
       thread-safe. This module makes direct pread and pwrite system calls and does NOT call the Samba VFS pread
       and pwrite interfaces.

EXAMPLES

       Straight forward use:

                   [cooldata]
                path = /data/ice
                aio read size = 1024
                aio write size = 1024
                vfs objects = aio_pthread

OPTIONS

       aio_pthread:aio num threads = INTEGER
           Limit the maximum number of threads per smbd that will be created in the thread pool to service IO
           requests.

           By default this is set to 100.

VERSION

       This man page is correct for version 4.0 of the Samba suite.

AUTHOR

       The original Samba software and related utilities were created by Andrew Tridgell. Samba is now developed
       by the Samba Team as an Open Source project similar to the way the Linux kernel is developed.