On 14/08/17 19:03, Dan Williams wrote: > On Mon, Aug 14, 2017 at 7:04 AM, Boaz Harrosh <boazh@xxxxxxxxxx> wrote: >> >> Thank you Jan, I'm patiently waiting for this MAP_SYNC flag since I asked for >> it in 2014. I'm so glad its time is finally do. >> <> >> 4] Once we have this flag. And properly implemented at least in one FS >> and optionally in /dev/pmemX we no longer have any justification for >> /dev/daxX and it can die a slow and happy death. > > I'm all for replacing /dev/dax with filesystem equivalent > functionality, but I don't think MAP_SYNC gets us fully there. That's > what the MAP_DIRECT proposal [1] is meant to address. > OK This is true. Could you please summarise for us the exact semantics of both proposed flags? That said I think the big difference is the movability of physical blocks underneath the mmap mapping. Now for swap files that is a problem. because of the deadlocks that can happen with memory needed if blocks start moving. But for an application like nvml? why does it care. Why can't an nvml image file not be cloned and COWed underneath the NVM application transparently. Sorry for being slow but I don't see why you need MAP_DIRECT from user-mode If you have MAP_SYNC. Please advise (not that the immutable patchset is not a very needed fixing) > [1]: https://lkml.org/lkml/2017/8/13/160 > Thanks Boaz
