On Wed, Feb 19, 2020 at 05:55:02PM +0000, Luis Chamberlain wrote: > On Wed, Feb 19, 2020 at 09:09:45AM -0800, Darrick J. Wong wrote: > > On Wed, Feb 19, 2020 at 02:38:24PM +0000, Luis Chamberlain wrote: > > > On Wed, Feb 19, 2020 at 03:32:27PM +0100, Carlos Maiolino wrote: > > > > On Wed, Feb 19, 2020 at 01:57:15PM +0000, Luis Chamberlain wrote: > > > > > I hear some folks still use CONFIG_XFS_RT, I was curious what was the > > > > > actual modern typical use case for it. I thought this was somewhat > > > > > realted to DAX use but upon a quick code inspection I see direct > > > > > realtionship. > > > > > > > > Hm, not sure if there is any other use other than it's original purpose of > > > > reducing latency jitters. Also XFS_RT dates way back from the day DAX was even a > > > > thing. But anyway, I don't have much experience using XFS_RT by myself, and I > > > > probably raised more questions than answers to yours :P > > > > > > What about another question, this would certainly drive the users out of > > > the corners: can we remove it upstream? > > > > My DVR and TV still use it to record video data. > > Is anyone productizing on that though? > > I was curious since most distros are disabling CONFIG_XFS_RT so I was > curious who was actually testing this stuff or caring about it. Most != All. We enabled it here, for development of future products. > > I've also been pushing the realtime volume for persistent memory devices > > because you can guarantee that all the expensive pmem gets used for data > > storage, that the extents will always be perfectly aligned to large page > > sizes, and that fs metadata will never defeat that alignment guarantee. > > For those that *are* using XFS in production with realtime volume with dax... > I wonder whatcha doing about all these tests on fstests which we don't > have a proper way to know if the test succeeded / failed [0] when an > external logdev is used, this then applies to regular external log dev > users as well [1]. Huh? How did we jump from realtime devices to external log files? > Which makes me also wonder then, what are the typical big users of the > regular external log device? > > Reviewing a way to address this on fstests has been on my TODO for > a while, but it begs the question of how much do we really care first. > And that's what I was really trying to figure out. > > Can / should we phase out external logdev / realtime dev? Who really is > caring about this code these days? Not many, I guess. :/ There seem to be a lot more tests these days that use dmflakey on the data device to simulate a temporary disk failure... but those aren't going to work for external log devices because they seem to assume that what we call the data device is also the log device. --D > [0] https://github.com/mcgrof/oscheck/blob/master/expunges/linux-next-xfs/xfs/unassigned/xfs_realtimedev.txt > [1] https://github.com/mcgrof/oscheck/blob/master/expunges/linux-next-xfs/xfs/unassigned/xfs_logdev.txt > > Luis
