On Mon, Nov 23, 2015 at 11:08:42PM +0100, Lutz Vieweg wrote: > On 11/23/2015 09:26 PM, Dave Chinner wrote: > >On Mon, Nov 23, 2015 at 12:05:53PM +0100, Lutz Vieweg wrote: > >>in June 2015 the article https://lwn.net/Articles/648292/ mentioned > >>upcoming support for limiting the quantity of buffered writes > >>using control groups. > >> > >>Back then, only ext4 was said to support that feature, with other > >>filesystems requiring some minor changes to do the same. > > > >Yes, changing the kernel code to support this functionality is about > >3 lines of code. > > Oh, I didn't expect it to be such a small change :-) > > >.... I haven't added support to XFS because I have no way of > >verifying the functionality works and that it continues to work as > >it is intended. i.e. we have no regression test coverage for cgroup > >aware writeback and until someone writes a set of regression tests > >that validate it's functionality works correctly it will remain this > >way. > > > >Writing code is trivial. Validating the code actually works as > >intended and doesn't silently get broken in the future is the > >hard part.... > > Understood, would you anyway be willing to publish such a > three-line-patch (outside of official releases) for those > daredevils (like me :-)) who'd be willing to give it a try? Just make the same mods to XFS as the ext4 patch here: http://www.spinics.net/lists/kernel/msg2014816.html > After all, this functionality is the last piece of the > "isolation"-puzzle that is missing from Linux to actually > allow fencing off virtual machines or containers from DOSing > each other by using up all I/O bandwidth... Yes, I know, but no-one seems to care enough about it to provide regression tests for it. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
