On Mon, May 13, 2013 at 07:40:03AM -0500, Seth Jennings wrote: > This patch adds the documentation file for the zswap functionality > > Signed-off-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx> > --- > Documentation/vm/zswap.txt | 72 ++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 72 insertions(+) > create mode 100644 Documentation/vm/zswap.txt > > diff --git a/Documentation/vm/zswap.txt b/Documentation/vm/zswap.txt > new file mode 100644 > index 0000000..88384b3 > --- /dev/null > +++ b/Documentation/vm/zswap.txt > @@ -0,0 +1,72 @@ > +Overview: > + > +Zswap is a lightweight compressed cache for swap pages. It takes pages that are > +in the process of being swapped out and attempts to compress them into a > +dynamically allocated RAM-based memory pool. If this process is successful, > +the writeback to the swap device is deferred and, in many cases, avoided > +completely. This results in a significant I/O reduction and performance gains > +for systems that are swapping. > + *Potentially* reduces IO and *potentially* shows performance gains. If the system is swap trashing, this may make things worse as you're generating the same amount of IO but having to compress/decompress as well. If there is less physical memory available because zswap pool is fragmented then an application may be pushed to swap prematurely and again, the performance is worse. Don't oversell this and the comment applies throughout the documentation. I also think it should be marked with a bit fat warning that it's a WIP and an additional warning that the performance characteristics are very heavily workload dependant. -- Mel Gorman SUSE Labs -- 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>