Messages in this thread | | | Date | Tue, 7 Jan 2014 07:58:30 -0800 | From | Christoph Hellwig <> | Subject | Re: Terrible performance of sequential O_DIRECT 4k writes in SAN environment. ~3 times slower then Solars 10 with the same HBA/Storage. |
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On Mon, Jan 06, 2014 at 09:10:32PM +0100, Jan Kara wrote: > This is likely a problem of Linux direct IO implementation. The thing is > that in Linux when you are doing appending direct IO (i.e., direct IO which > changes file size), the IO is performed synchronously so that we have our > life simpler with inode size update etc. (and frankly our current locking > rules make inode size update on IO completion almost impossible). Since > appending direct IO isn't very common, we seem to get away with this > simplification just fine...
Shouldn't be too much of a problem at least for XFS and maybe even ext4 with the workqueue based I/O end handler. For XFS we protect size updates by the ilock which we already taken in that handler, not sure what ext4 would do there.
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