The program xen-tmem-list-parse parses the output of xm/xl tmem-list
into human-readable format. A missing NULL terminator sometimes
causes garbage to be spewed where the two-letter pool type
should be output.
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
Add "page deduplication" capability (with optional compression
and trailing-zero elimination) to Xen's tmem.
(Transparent to tmem-enabled guests.) Ephemeral pages
that have the exact same content are "combined" so that only
one page frame is needed. Since ephemeral pages are essentially
read-only, no C-O-W (and thus no equivalent of swapping) is
necessary. Deduplication can be combined with compression
or "trailing zero elimination" for even more space savings.
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Tmem can share clean page cache pages for Linux domains
in a virtual cluster (currently only the ocfs2 filesystem
has a patch on the Linux side). So when one domain
"puts" (evicts) a page, any domain in the cluster can
"get" it, thus saving disk reads. This functionality
is already present; these are only bug fixes.
- fix bugs when an SE pool is destroyed
- fixes in parsing tool for xm tmem-list output for SE pools
- incorrect locking in one case for destroying an SE pool
- clearer verbosity for transfer when an SE pool is destroyed
- minor cleanup: merge routines that are mostly duplicate
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Tmem, when called from a tmem-capable (paravirtualized) guest, makes
use of otherwise unutilized ("fallow") memory to create and manage
pools of pages that can be accessed from the guest either as
"ephemeral" pages or as "persistent" pages. In either case, the pages
are not directly addressible by the guest, only copied to and fro via
the tmem interface. Ephemeral pages are a nice place for a guest to
put recently evicted clean pages that it might need again; these pages
can be reclaimed synchronously by Xen for other guests or other uses.
Persistent pages are a nice place for a guest to put "swap" pages to
avoid sending them to disk. These pages retain data as long as the
guest lives, but count against the guest memory allocation.
Tmem pages may optionally be compressed and, in certain cases, can be
shared between guests. Tmem also handles concurrency nicely and
provides limited QoS settings to combat malicious DoS attempts.
Save/restore and live migration support is not yet provided.
Tmem is primarily targeted for an x86 64-bit hypervisor. On a 32-bit
x86 hypervisor, it has limited functionality and testing due to
limitations of the xen heap. Nearly all of tmem is
architecture-independent; three routines remain to be ported to ia64
and it should work on that architecture too. It is also structured to
be portable to non-Xen environments.
Tmem defaults off (for now) and must be enabled with a "tmem" xen boot
option (and does nothing unless a tmem-capable guest is running). The
"tmem_compress" boot option enables compression which takes about 10x
more CPU but approximately doubles the number of pages that can be
stored.
Tmem can be controlled via several "xm" commands and many interesting
tmem statistics can be obtained. A README and internal specification
will follow, but lots of useful prose about tmem, as well as Linux
patches, can be found at http://oss.oracle.com/projects/tmem .
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Dan Magenheimer
Keir Fraser