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    SubjectRe: [PATCH] Make swap accounting default behavior configurable
    On Tue, 16 Nov 2010 12:46:15 -0800
    Andrew Morton <akpm@linux-foundation.org> wrote:

    > On Tue, 16 Nov 2010 11:17:26 +0100
    > Michal Hocko <mhocko@suse.cz> wrote:
    >
    > > Hi Andrew,
    > > could you consider the following patch for the Linus tree, please?
    > > The discussion took place in this email thread
    > > http://lkml.org/lkml/2010/11/10/114.
    > > The patch is based on top of 151f52f09c572 commit in the Linus tree.
    > >
    > > Please let me know if there I should route this patch through somebody
    > > else.
    > >
    > > Thanks!
    > >
    > > ---
    > > >From 30238aaec758988493af793939f14b0ba83dc4b3 Mon Sep 17 00:00:00 2001
    > > From: Michal Hocko <mhocko@suse.cz>
    > > Date: Wed, 10 Nov 2010 13:30:04 +0100
    > > Subject: [PATCH] Make swap accounting default behavior configurable
    > >
    > > Swap accounting can be configured by CONFIG_CGROUP_MEM_RES_CTLR_SWAP
    > > configuration option and then it is turned on by default. There is
    > > a boot option (noswapaccount) which can disable this feature.
    > >
    > > This makes it hard for distributors to enable the configuration option
    > > as this feature leads to a bigger memory consumption and this is a no-go
    > > for general purpose distribution kernel. On the other hand swap
    > > accounting may be very usuful for some workloads.
    >
    > This patch is needed by distros, and distros use the -stable tree, I
    > assume. Do you see reasons why this patch should be backported into
    > -stable, so distros don't need to patch it themselves? If so, any
    > particular kernel versions? 2.6.37?
    >
    > > This patch adds a new configuration option which controls the default
    > > behavior (CGROUP_MEM_RES_CTLR_SWAP_ENABLED). If the option is selected
    > > then the feature is turned on by default.
    > >
    > > It also adds a new boot parameter swapaccount which (contrary to
    > > noswapaccount) enables the feature. (I would consider swapaccount=yes|no
    > > semantic with removed noswapaccount parameter much better but this
    > > parameter is kind of API which might be in use and unexpected breakage
    > > is no-go.)
    > >
    > > The default behavior is unchanged (if CONFIG_CGROUP_MEM_RES_CTLR_SWAP is
    > > enabled then CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED is enabled as well)
    > >
    > > Signed-off-by: Michal Hocko <mhocko@suse.cz>
    > > Acked-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
    > > ---
    > > Documentation/kernel-parameters.txt | 3 +++
    > > init/Kconfig | 13 +++++++++++++
    > > mm/memcontrol.c | 15 ++++++++++++++-
    > > 3 files changed, 30 insertions(+), 1 deletions(-)
    > >
    > > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
    > > index ed45e98..14eafa5 100644
    > > --- a/Documentation/kernel-parameters.txt
    > > +++ b/Documentation/kernel-parameters.txt
    > > @@ -2385,6 +2385,9 @@ and is between 256 and 4096 characters. It is defined in the file
    > > improve throughput, but will also increase the
    > > amount of memory reserved for use by the client.
    > >
    > > + swapaccount [KNL] Enable accounting of swap in memory resource
    > > + controller. (See Documentation/cgroups/memory.txt)
    >
    > So we have swapaccount and noswapaccount. Ho hum, "swapaccount=[1|0]"
    > would have been better.
    >
    I suggested to keep "noswapaccount" for compatibility.
    If you and other guys don't like having two parameters, I don't stick to
    the old parameter.

    Thanks,
    Daisuke Nishimura.


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