On Thu, Oct 16, 2014 at 09:39:08AM +0200, Mathieu Desnoyers wrote: > First of all, thanks a lot for this patchset! Secondly, I must voice out > that you really need to work on your marketing skills. What your > changelog does not show is that this feature is tremendously useful > *today* in the following use-case: > > - On *any* platform for which you can teach the BIOS not to clear memory > on soft reboot, > - Use a kernel argument to restrain it to portion of memory at boot > (e.g. 15GB out of 16GB), > - Create an ext4 or ext2 filesystem in this available memory area, > - Mount it with DAX flags, Yes, I definitely suck at technical marketing. I was thinking that "NV-DIMMs" were the new hotness, and definitely available today, and so advertising support for them was the best way to go. I personally do use your use case for testing DAX, but it didn't occur to me that it would have real-world usages. > >From there, you can do lots of interesting stuff. In my use-case, I > would love to use it to mmap LTTng kernel/userspace tracer buffers, so > we can extract them after a soft reboot and analyze a system crash. > > My recommendation would be to rename this patchset as e.g. > > "DAX: Page cache bypass for in-memory persistent filesystems" > > which might attract more interest from reviewers and maintainers, since > they can try it out today on commodity hardware. Also, pointing out to > ext4 specifically in the patchset introduction title does not reflect > the content accurately, since there is also ext2 implementation within > the series. Well ... ext2 already has the 'xip' implementation which probably works well enough for enough of the time. Most people probably won't hit the races it has. > One thing I would really like to see is a Documentation file that > explains how to setup the kernel so it leaves a memory area free at the > end of the physical address space, and how to setup a filesystem into > it. Perhaps it already exists, in this case, pointing to it in the > patchset introduction changelog would be helpful. (IOW, answering the > question: how can someone test this today on commodity hardware ?). > Also, if there are ways to setup pstore or such to achieve something > similar of a wider range of systems, it would be nice to see > documentation (or links to doc) explaining how to configure this. I think that documentation properly belongs to the 'pmem' block driver that Ross has been posting. Here's 1/4, which contains some documentation, but I think you're after something more detailed: http://marc.info/?l=linux-fsdevel&m=140917398012020&w=2 > I'll try to review your patchset soon, however keeping in mind that it > would be best to have mm experts having a look into it. Yes, mm experts have many demands on their time, unfortunately :-( -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>