On Mon, Oct 16, 2017 at 01:00:32PM +0300, Avi Kivity wrote: > On 10/16/2017 01:00 AM, Dave Chinner wrote: > >On Sun, Oct 15, 2017 at 12:36:03PM +0300, Avi Kivity wrote: > >>On 10/15/2017 01:42 AM, Dave Chinner wrote: > >>>On Fri, Oct 13, 2017 at 11:13:24AM +0300, Avi Kivity wrote: > >>Even better would be if XFS would detect the sequential write and > >>start allocating ahead of it. > >That's what delayed allocation does with buffered IO. We > >specifically do not do that with direct IO because it's direct IO > >and we only do exactly what the IO the user submits requires us to > >do. > > > >As it is, I'm not sure that it would gain us anything over extent > >size hints because they are effectively doing exactly the same thing > >(i.e. allocate ahead) on every write that hits a hole beyond > >EOF when extending the file.... > > If I understand correctly, you do get momentary serialization when > you cross a hint boundary, while with allocate ahead, you would not. Allocate ahead still requires a threshold to be crossed to trigger allocation. So it doesn't get rid of allocation, it just changes what IO triggers it. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
