1VFS_AIO_PTHREAD(8)        System Administration tools       VFS_AIO_PTHREAD(8)
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NAME

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

9       vfs objects = aio_pthread
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DESCRIPTION

12       This VFS module is part of the samba(7) suite.
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14       The aio_pthread VFS module enables asynchronous I/O for Samba on
15       platforms which have the pthreads API available, without using the
16       Posix AIO interface. Posix AIO can suffer from severe limitations. For
17       example, on some Linux versions the real-time signals that it uses are
18       broken under heavy load. Other systems only allow AIO when special
19       kernel modules are loaded or only allow a certain system-wide amount of
20       async requests being scheduled. Systems based on glibc (most Linux
21       systems) only allow a single outstanding request per file descriptor
22       which essentially makes Posix AIO useless on systems using the glibc
23       implementation.
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25       To work around all these limitations, the aio_pthread module was
26       written. It uses a pthread pool instead of the internal Posix AIO
27       interface to allow read and write calls to be process asynchronously. A
28       pthread pool is created which expands dynamically by creating new
29       threads as work is given to it to a maximum of 100 threads per smbd
30       process. To change this limit see the "aio num threads" parameter
31       below. New threads are not created if idle threads are available when a
32       new read or write request is received, the new work is given to an
33       existing idle thread. Threads terminate themselves if idle for one
34       second.
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36       Note that the smb.conf parameters aio read size and aio write size must
37       also be set appropriately for this module to be active.
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39       This module MUST be listed last in any module stack as the Samba VFS
40       pread/pwrite interface is not thread-safe. This module makes direct
41       pread and pwrite system calls and does NOT call the Samba VFS pread and
42       pwrite interfaces.
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EXAMPLES

45       Straight forward use:
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47                   [cooldata]
48                path = /data/ice
49                aio read size = 1024
50                aio write size = 1024
51                vfs objects = aio_pthread
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OPTIONS

54       aio_pthread:aio num threads = INTEGER
55           Limit the maximum number of threads per smbd that will be created
56           in the thread pool to service IO requests.
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58           By default this is set to 100.
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VERSION

61       This man page is correct for version 3.6.3 of the Samba suite.
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AUTHOR

64       The original Samba software and related utilities were created by
65       Andrew Tridgell. Samba is now developed by the Samba Team as an Open
66       Source project similar to the way the Linux kernel is developed.
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70Samba 3.6                         04/11/2016                VFS_AIO_PTHREAD(8)
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