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[157.230.128.187]) by smtp.gmail.com with ESMTPSA id t16sm322570pgo.80.2020.02.19.09.55.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Feb 2020 09:55:03 -0800 (PST) Received: by 42.do-not-panic.com (Postfix, from userid 1000) id 5B2FD402D7; Wed, 19 Feb 2020 17:55:02 +0000 (UTC) Date: Wed, 19 Feb 2020 17:55:02 +0000 From: Luis Chamberlain To: "Darrick J. Wong" Cc: Richard Wareing , linux-xfs@vger.kernel.org, Anthony Iliopoulos , Yong Sun Subject: Re: Modern uses of CONFIG_XFS_RT Message-ID: <20200219175502.GS11244@42.do-not-panic.com> References: <20200219135715.GZ30113@42.do-not-panic.com> <20200219143227.aavgzkbuazttpwky@andromeda> <20200219143824.GR11244@42.do-not-panic.com> <20200219170945.GN9506@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200219170945.GN9506@magnolia> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org 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. > 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]. 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? [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