I read this paper "Transcendent Memoryand Linux" by Dan Magenheimer,Chris Mason,Dave McCracken,Kurt Hackel. After reading this ,I think that tmem implementation is specific to filesystem as if changes are also done in fs/. which are the filesystems supported by tmem? and which are the upcoming filesystems getting tmem support ? So does it shares only data segment and not the code segment?as if many VMs of same type running on same host can also share Code-segment-pages. Let me correct if I am wrong. -- With Regards, Ashwin Vasani B.E. (Fourth Year) Computer Engineering, Pune Institute of Computer Technology. +91 9960405802 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Vasiliy G Tolstov
2010-Sep-11 21:29 UTC
[Xen-devel] Re: [Tmem-devel] Queries on Filesystem Support
On Sun, 2010-09-12 at 01:14 +0530, ash win wrote:> I read this paper "Transcendent Memoryand Linux" by Dan > Magenheimer,Chris Mason,Dave McCracken,Kurt Hackel. > After reading this ,I think that tmem implementation is specific to > filesystem as if changes are also done in fs/. > which are the filesystems supported by tmem? and which are the > upcoming filesystems getting tmem support ?As i known, btrfs, ocfs2, ext3, ext4. -- Vasiliy G Tolstov <v.tolstov@selfip.ru> Selfip.Ru _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi Ashwin -- Yes, the Linux-side tmem support is specific to certain Linux filesystems. For an explanation of this, see FAQ #2 in: http://lkml.org/lkml/2010/9/3/383 Vasiliy is correct that ext3, ext4, btrfs, and ocfs2 are currently supported. Other filesystems should be easy to add, but must be extensively tested. The xfs filesystem would be next, but I haven''t tried it. As you know, tmem supports ephemeral pages and peristent pages. In Linux these are called "cleancache" and "frontswap" (as the Linux patches are layered so they can be used for functionality other than tmem). Cleancache works for any clean pages that are "evicted" by Linux, so this may be code or data pages, but only "mapped" pages (i.e. pages that are obtained from disk or match pages that have been written to disk). If many VMs on the same host share a clustered filesystem, the entire ephemeral pool corresponding to that filesystem is shared. If the VMs do not share a clustered filesystem and "tmem-dedup" is enabled, identical pages are deduplicated. Since ephemeral pages in tmem are essentially read-only, this is different from classic "transparent page sharing". Thanks, Dan> -----Original Message----- > From: ash win [mailto:ash_win012006@yahoo.com] > Sent: Saturday, September 11, 2010 1:45 PM > To: tmem-devel@oss.oracle.com > Cc: Kurt Hackel; Dan Magenheimer; Xen-devel@lists.xensource.com; Chris > Mason; Dave Mccracken > Subject: [Xen-devel] Queries on Filesystem Support > > I read this paper "Transcendent Memoryand Linux" by Dan > Magenheimer,Chris Mason,Dave McCracken,Kurt Hackel. > After reading this ,I think that tmem implementation is specific to > filesystem as if changes are also done in fs/. > which are the filesystems supported by tmem? and which are the > upcoming filesystems getting tmem support ? > So does it shares only data segment and not the code segment?as if > many VMs of same type running on same host can also share Code-segment- > pages. > Let me correct if I am wrong. > > -- > With Regards, > Ashwin Vasani > B.E. (Fourth Year) > Computer Engineering, > Pune Institute of Computer Technology. > +91 9960405802 > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel