vfs_aio_linux — implement async I/O in Samba vfs using Linux kernel aio calls
vfs objects = aio_linux
This VFS module is part of the samba(7) suite.
The aio_linux
VFS module enables asynchronous
I/O for Samba on Linux kernels that have the kernel AIO calls 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_linux module was written. It uses the Linux kernel AIO interface instead of the internal Posix AIO interface to allow read and write calls to be processed asynchronously. A queue size of 128 events is used by default. To change this limit set the "aio num events" parameter below.
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.
Straight forward use:
[cooldata]
path = /data/ice
aio read size = 1024
aio write size = 1024
vfs objects = aio_linux