From: Vladimir Murzin <murzin.v@gmail.com>
To: Dan Streetman <ddstreet@ieee.org>
Cc: linux-mm@kvack.org, Seth Jennings <sjennings@variantweb.net>,
linux-kernel <linux-kernel@vger.kernel.org>,
Bob Liu <bob.liu@oracle.com>, Minchan Kim <minchan@kernel.org>,
Weijie Yang <weijie.yang@samsung.com>
Subject: Re: [PATCH] mm/zswap: change params from hidden to ro
Date: Fri, 22 Nov 2013 08:38:54 +0100 [thread overview]
Message-ID: <20131122073851.GB1853@hp530> (raw)
In-Reply-To: <CALZtONA81=R4abFMpMMtDZKQe0s-8+JxvEfZO3NEZ910VwRDmw@mail.gmail.com>
On Wed, Nov 20, 2013 at 12:52:47PM -0500, Dan Streetman wrote: > On Wed, Nov
20, 2013 at 12:33 PM, Vladimir Murzin <murzin.v@gmail.com> wrote: > > Hi Dan!
> >
> > On Wed, Nov 20, 2013 at 11:38:42AM -0500, Dan Streetman wrote:
> >> The "compressor" and "enabled" params are currently hidden,
> >> this changes them to read-only, so userspace can tell if
> >> zswap is enabled or not and see what compressor is in use.
> >
> > Could you elaborate more why this pice of information is necessary for
> > userspace?
>
> For anyone interested in zswap, it's handy to be able to tell if it's
> enabled or not ;-) Technically people can check to see if the zswap
> debug files are in /sys/kernel/debug/zswap, but I think the actual
> "enabled" param is more obvious. And the compressor param is really
> the only way anyone from userspace can see what compressor's being
> used; that's helpful to know for anyone that might want to be using a
> non-default compressor.
So, it is needed for user not userspace? I tend to think that users are smart
enough to check cmdline for that.
AFAICS module_param exist here to provide simplest ability to handle the
setting via cmdline. zsawap is not able to be loaded as a module for now. If
it could, than there was reason to check which params were used while module
loading and guess how they affected zswap state.
>
> And of course, eventually we'll want to make the params writable, so
> the compressor can be changed dynamically, and zswap can be enabled or
> disabled dynamically (or at least enabled after boot).
module_params is not the best place to handle this, because they do not
provide any hooks for handling write unless I missed something. However,
making zswap state dynamically adjustable require not only setting the
numbers, but handling the correctness switching from one state to another.
Vladimir
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next prev parent reply other threads:[~2013-11-22 7:39 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-20 16:38 Dan Streetman
2013-11-20 17:33 ` Vladimir Murzin
2013-11-20 17:52 ` Dan Streetman
2013-11-21 3:12 ` Weijie Yang
2013-11-21 22:36 ` Dan Streetman
2013-11-22 7:38 ` Vladimir Murzin [this message]
2013-11-22 17:18 ` Dan Streetman
2013-11-24 14:15 ` Vladimir Murzin
2013-11-22 17:21 ` Seth Jennings
2013-12-13 20:56 ` Dan Streetman
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