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. 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. -------------------------------------------------------- ZTE Information Security Notice: The information contained in this mail (and any attachment transmitted herewith) is privileged and confidential and is intended for the exclusive use of the addressee(s). If you are not an intended recipient, any disclosure, reproduction, distribution or other dissemination or use of the information contained is strictly prohibited. If you have received this mail in error, please delete it and notify us immediately.
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