![]() That mix O_DSYNC overwrites with other write IO as we won't beįlushing the entire device cache on every DSYNC overwrite IOįs/iomap.c | 38 +++++++++++++++++++++++++++++++++-Ģ files changed, 38 insertions(+), 5 deletions(-)ĭarrick J. ![]() However, the benefits will be higher on workloads Instead uses FUA (confirmed via blktrace), and performance improvesĪ bit as a result. The patched code clearly doesn't send cache flushes anymore, but Kernel time write()s write iops Write b/w # xfs_io -fd -c "pwrite -V 1 -D 0 32m" /mnt/scratch/boo (sequential 4k overwrites in 32MB file) had the following results: On a FUA enabled device, a synchronous direct IO write workload This means the filesystemĭoesn't have to guess when cache flushes are necessary now. Iomap_dio_rw() always responsible for issuing generic_write_sync() When REQ_FUA is issued, otherwise it will still throw a cache flush Have to stop issuing generic_write_sync() calls from the XFS code Now that iomap_dio_rw() is determining if REQ_FUA can be used, we This makes pure direct IO data writeīehaviour identical to the way block devices use REQ_FUA to provide Generic_write_sync() call in IO completion and hence avoid The IO mapping is not dirty, then we can use a FUA write to provideĭatasync semantics. Hence if we have been returned a mapped extent that is not new and IO writes, we can use it to determine if we need to flush metadata Requires a metadata flush - this is currently used by DAX to ensureĮxtent modi$fication as stable in page fault operations. ![]() We know from teh IOMAP_F_DIRTY flag as to whether a specific inode If we are overwriting existing data, there are no metadata changes Have to flush metadata changes along with the data write. If we are doing direct IO writes with datasync semantics, we often To: iomap: Use FUA for pure data O_DSYNC DIO writesĭave Chinner March 1, 2018, 1:41 a.m. Received: from dave by with local (Exim 4.90_1) net" rhost-flags-OK-OK-OK-OK)īy with ESMTP id S932134AbeCABmA (ORCPT Received: from ( )īy mail.wl. (Postfix) with ESMTP id 0F36528F48 X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI X-Spam-Checker-Version: SpamAssassin 3.3.1 () on Received: by mail.wl. (Postfix, from userid 486) Received: from mail.wl. (localhost )īy mail.wl. (Postfix) with ESMTP id B519927C0B Received: from mail.wl. (īy (Postfix) with ESMTP id
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