vfs_aio_pthread - implement async I/O in Samba vfs using a pthread pool
vfs objects = aio_pthread
System Administration tools VFS_AIO_PTHREAD(8)
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.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+-----------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------------+
|Availability | service/network/samba |
+---------------+-----------------------+
|Stability | Volatile |
+---------------+-----------------------+
NOTES
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from
https://download.samba.org/pub/samba/stable/samba-4.7.6.tar.gz
Further information about this software can be found on the open source
community website at http://www.samba.org/.
Samba 4.7 08/01/2018 VFS_AIO_PTHREAD(8)