On Fri, Feb 20, 2015 at 07:49:16PM -0800, Hugh Dickins wrote: > I warned last month that I have been working on "huge tmpfs": > an implementation of Transparent Huge Page Cache in tmpfs, > for those who are tired of the limitations of hugetlbfs. > > Here's a fully working patchset, against v3.19 so that you can give it > a try against a stable base. I've not yet studied how well it applies > to current git: probably lots of easily resolved clashes with nonlinear > removal. Against mmotm, the rmap.c differences looked nontrivial. > > Fully working? Well, at present page migration just keeps away from > these teams of pages. And once memory pressure has disbanded a team > to swap it out, there is nothing to put it together again later on, > to restore the original hugepage performance. Those must follow, > but no thought yet (khugepaged? maybe). > > Yes, I realize there's nothing yet under Documentation, nor fs/proc > beyond meminfo, nor other debug/visibility files: must follow, but > I've cared more to provide the basic functionality. > > I don't expect to update this patchset in the next few weeks: now that > it's posted, my priority is look at other people's work before LSF/MM; > and in particular, of course, your (Kirill's) THP refcounting redesign. I scanned through the patches to get general idea on how it works. I'm not sure that I will have time and will power to do proper code-digging before the summit. I found few bugs in my patchset which I want to troubleshoot first. One thing I'm not really comfortable with is introducing yet another way to couple pages together. It's less risky in short term than my approach -- fewer existing codepaths affected, but it rises maintaining cost later. Not sure it's what we want. After Johannes' work which added exceptional entries to normal page cache I hoped to see shmem/tmpfs implementation moving toward generic page cache. But this patchset is step in other direction -- it makes shmem/tmpfs even more special-cased. :( Do you have any insights on how this approach applies to real filesystems? I don't think there's any show stopper, but better to ask early ;) -- Kirill A. Shutemov -- 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>