Sorry for the delay in response.
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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