On Wed, Jan 15, 2020 at 09:39:35PM -0800, Darrick J. Wong wrote: > On Wed, Jan 15, 2020 at 02:38:21PM -0800, Ira Weiny wrote: > > On Wed, Jan 15, 2020 at 12:10:50PM -0800, Dan Williams wrote: > > > On Wed, Jan 15, 2020 at 11:45 AM Ira Weiny <ira.weiny@xxxxxxxxx> wrote: > > > > > > > > On Wed, Jan 15, 2020 at 09:38:34AM -0800, Darrick J. Wong wrote: > > > > > On Wed, Jan 15, 2020 at 12:37:15PM +0100, Jan Kara wrote: > > > > > > On Fri 10-01-20 11:29:31, ira.weiny@xxxxxxxxx wrote: > > > > > > > From: Ira Weiny <ira.weiny@xxxxxxxxx> > > > > > > > > > [snip] > > > > Sure, but for now I think referencing mmap for details on MAP_SYNC works. > > > > I suspect that we may have some word smithing once I get this series in and we > > submit a change to the statx man page itself. Can I move forward with the > > following for this patch? > > > > <quote> > > STATX_ATTR_DAX > > > > The file is in the DAX (cpu direct access) state. DAX state > > Hmm, now that I see it written out, I <cough> kind of like "DAX mode" > better now. :/ > > "The file is in DAX (CPU direct access) mode. DAX mode attempts..." Sure... now you tell me... ;-) Seriously, we could use mode here in the man page as this is less confusing to say "DAX mode". But I think the code should still use 'state' because mode is just too overloaded. You were not the only one who was thrown by my use of mode and I don't want that confusion when we look at this code 2 weeks from now... https://www.reddit.com/r/ProgrammerHumor/comments/852og2/only_god_knows/ ;-) > > > attempts to minimize software cache effects for both I/O and > > memory mappings of this file. It requires a file system which > > has been configured to support DAX. > > > > DAX generally assumes all accesses are via cpu load / store > > instructions which can minimize overhead for small accesses, but > > may adversely affect cpu utilization for large transfers. > > > > File I/O is done directly to/from user-space buffers and memory > > mapped I/O may be performed with direct memory mappings that > > bypass kernel page cache. > > > > While the DAX property tends to result in data being transferred > > synchronously, it does not give the same guarantees of > > synchronous I/O where data and the necessary metadata are > > transferred together. > > (I'm frankly not sure that synchronous I/O actually guarantees that the > metadata has hit stable storage...) I'll let you and Dan work this one out... ;-) Ira
