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Date: Wed, 31 Oct 2012 08:15:17 -0700 (PDT)
From: Dan Magenheimer <dan.magenheimer@...cle.com>
To: Dan Magenheimer <dan.magenheimer@...cle.com>,
devel@...uxdriverproject.org, linux-kernel@...r.kernel.org,
gregkh@...uxfoundation.org, linux-mm@...ck.org, ngupta@...are.org,
konrad.wilk@...cle.com, sjenning@...ux.vnet.ibm.com,
minchan@...nel.org, fschmaus@...il.com,
Andor Daam <andor.daam@...glemail.com>, ilendir@...glemail.com,
akpm@...ux-foundation.org, mgorman@...e.de
Subject: RE: [PATCH 0/5] enable all tmem backends to be built and loaded as
modules
Apologies... I misspelled the family name of one of the
Erlangen University authors of the first two patches
in this patchset, so any reply-alls to any of the
patch posts will see a bounce. If you reply-all to any
of these patches, kindly change one of the recipients
to:
andor.daam@...glemail.com (was misspelled andor.damm)
I regret the inconvenience... :-(
> -----Original Message-----
> From: Dan Magenheimer [mailto:dan.magenheimer@...cle.com]
> Sent: Wednesday, October 31, 2012 9:08 AM
> To: devel@...uxdriverproject.org; linux-kernel@...r.kernel.org; gregkh@...uxfoundation.org; linux-
> mm@...ck.org; ngupta@...are.org; konrad.wilk@...cle.com; sjenning@...ux.vnet.ibm.com;
> minchan@...nel.org; dan.magenheimer@...cle.com; fschmaus@...il.com; andor.damm@...glemail.com;
> ilendir@...glemail.com; akpm@...ux-foundation.org; mgorman@...e.de
> Subject: [PATCH 0/5] enable all tmem backends to be built and loaded as modules
>
> Since various parts of transcendent memory ("tmem") [1] were first posted in
> 2009, reviewers have suggested that various tmem features should be built
> as a module and enabled by loading the module, rather than the current clunky
> method of compiling as a built-in and enabling via boot parameter. Due
> to certain tmem initialization steps, that was not feasible at the time.
>
> [1] http://lwn.net/Articles/454795/
>
> This patchset allows each of the three merged transcendent memory
> backends (zcache, ramster, Xen tmem) to be used as modules by first
> enabling transcendent memory frontends (cleancache, frontswap) to deal
> with "lazy initialization" and, second, by adding the necessary code for
> the backends to be built and loaded as modules.
>
> The original mechanism to enable tmem backends -- namely to hardwire
> them into the kernel and select/enable one with a kernel boot
> parameter -- is retained but should be considered deprecated. When
> backends are loaded as modules, certain knobs will now be
> properly selected via module_params rather than via undocumented
> kernel boot parameters. Note that module UNloading is not yet
> supported as it is lower priority and will require significant
> additional work.
>
> The lazy initialization support is necessary because filesystems
> and swap devices are normally mounted early in boot and these
> activites normally trigger tmem calls to setup certain data structures;
> if the respective cleancache/frontswap ops are not yet registered
> by a back end, the tmem setup would fail for these devices and
> cleancache/frontswap would never be enabled for them which limits
> much of the value of tmem in many system configurations. Lazy
> initialization records the necessary information in cleancache/frontswap
> data structures and "replays" it after the ops are registered
> to ensure that all filesystems and swap devices can benefit from
> the loaded tmem backend.
>
> Patches 1 and 2 are the original [2] patches to cleancache and frontswap
> proposed by Erlangen University, but rebased to 3.7-rcN plus a couple
> of bug fixes I found necessary to run properly. I have not attempted
> any code cleanup. I have also added defines to ensure at runtime
> that backends are not loaded as modules if the frontend patches are not
> yet merged; this is useful to avoid any build dependency (since the
> frontends may be merged into linux-next through different trees and
> at different times than some backends) and once the entire patchset
> is safely merged, these defines/ifdefs can be removed.
>
> [2] http://www.spinics.net/lists/linux-mm/msg31490.html
>
> Patch 3 enables module support for zcache2. Zsmalloc support
> has not yet been merged into zcache2 but, once merged, could now
> easily be selected via a module_param.
>
> Patch 4 enables module support for ramster. Ramster will now be
> enabled with a module_param to zcache2.
>
> Patch 5 enables module support for the Xen tmem shim. Xen
> self-ballooning and frontswap-selfshrinking are also "lazily"
> initialized when the Xen tmem shim is loaded as a module, unless
> explicitly disabled by module_params.
>
> Signed-off-by: Dan Magenheimer <dan.magenheimer@...cle.com>
>
> ---
> Diffstat:
>
> drivers/staging/ramster/Kconfig | 6 +-
> drivers/staging/ramster/Makefile | 11 +-
> drivers/staging/ramster/ramster.h | 6 +-
> drivers/staging/ramster/ramster/nodemanager.c | 9 +-
> drivers/staging/ramster/ramster/ramster.c | 29 +++-
> drivers/staging/ramster/ramster/ramster.h | 2 +-
> .../staging/ramster/ramster/ramster_nodemanager.h | 2 +
> drivers/staging/ramster/tmem.c | 6 +-
> drivers/staging/ramster/tmem.h | 8 +-
> drivers/staging/ramster/zcache-main.c | 61 +++++++-
> drivers/staging/ramster/zcache.h | 2 +-
> drivers/xen/Kconfig | 4 +-
> drivers/xen/tmem.c | 56 ++++++--
> drivers/xen/xen-selfballoon.c | 13 +-
> include/linux/cleancache.h | 1 +
> include/linux/frontswap.h | 1 +
> include/xen/tmem.h | 8 +
> mm/cleancache.c | 157 +++++++++++++++++--
> mm/frontswap.c | 70 ++++++++-
> 19 files changed, 379 insertions(+), 73 deletions(-)
--
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