Sorry for the delay in response.
On 01/15/2016 02:34 PM, li.ping...@zte.com.cn wrote:
GLUSTERFS_WRITE_IS_APPEND Setting in afr_writev function at glusterfs
client end makes the posix_writev in the server end deal IO write
fops from parallel to serial in consequence.
i.e. multiple io-worker threads carrying out IO write fops are
blocked in posix_writev to execute final write fop pwrite/pwritev in
__posix_writev function ONE AFTER ANOTHER.
For example:
thread1: iot_worker -> ... -> posix_writev() |
thread2: iot_worker -> ... -> posix_writev() |
thread3: iot_worker -> ... -> posix_writev() -> __posix_writev()
thread4: iot_worker -> ... -> posix_writev() |
there are 4 iot_worker thread doing the 128KB IO write fops as above,
but only one can execute __posix_writev function and the others have
to wait.
however, if the afr volume is configured on with storage.linux-aio
which is off in default, the iot_worker will use posix_aio_writev
instead of posix_writev to write data.
the posix_aio_writev function won't be affected by
GLUSTERFS_WRITE_IS_APPEND, and the AFR volume write performance goes up.
I think this is a bug :-(.
So, my question is whether AFR volume could work fine with
storage.linux-aio configuration which bypass the
GLUSTERFS_WRITE_IS_APPEND setting in afr_writev,
and why glusterfs keeps posix_aio_writev different from posix_writev ?
Any replies to clear my confusion would be grateful, and thanks in
advance.
What is the workload you have? multiple writers on same file workloads?
Pranith
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