<font size=2 face="sans-serif">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.</font>
<br>
<br><font size=2 face="sans-serif">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.
</font>
<br>
<br><font size=2 face="sans-serif">For example:</font>
<br>
<br><font size=2 face="sans-serif">thread1: iot_worker -> ... ->
posix_writev() |</font>
<br><font size=2 face="sans-serif">thread2: iot_worker -> ... ->
posix_writev() |</font>
<br><font size=2 face="sans-serif">thread3: iot_worker -> ... ->
posix_writev() -> __posix_writev() </font>
<br><font size=2 face="sans-serif">thread4: iot_worker -> ... ->
posix_writev() |</font>
<br>
<br><font size=2 face="sans-serif">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.</font>
<br>
<br><font size=2 face="sans-serif">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.</font>
<br><font size=2 face="sans-serif">the posix_aio_writev function won't
be affected by GLUSTERFS_WRITE_IS_APPEND, and the AFR volume write performance
goes up.</font>
<br>
<br><font size=2 face="sans-serif">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, </font>
<br><font size=2 face="sans-serif">and why glusterfs keeps posix_aio_writev
different from posix_writev ?</font>
<br>
<br><font size=2 face="sans-serif">Any replies to clear my confusion would
be grateful, and thanks in advance.<br>
</font>
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