From: Minchan Kim <minchan@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Hugh Dickins <hughd@google.com>, Shaohua Li <shli@kernel.org>,
Jerome Marchand <jmarchan@redhat.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Dan Streetman <ddstreet@ieee.org>,
Nitin Gupta <ngupta@vflare.org>,
Luigi Semenzato <semenzato@google.com>,
juno.choi@lge.com
Subject: Re: [PATCH v1 4/5] zram: add swap full hint
Date: Wed, 24 Sep 2014 16:57:12 +0900 [thread overview]
Message-ID: <20140924075712.GA3181@bbox> (raw)
In-Reply-To: <20140923141755.b7854bae484cfe434797be02@linux-foundation.org>
On Tue, Sep 23, 2014 at 02:17:55PM -0700, Andrew Morton wrote:
> On Tue, 23 Sep 2014 13:56:02 +0900 Minchan Kim <minchan@kernel.org> wrote:
>
> > >
> > > > +#define ZRAM_FULLNESS_PERCENT 80
> > >
> > > We've had problems in the past where 1% is just too large an increment
> > > for large systems.
> >
> > So, do you want fullness_bytes like dirty_bytes?
>
> Firstly I'd like you to think about whether we're ever likely to have
> similar granularity problems with this tunable. If not then forget
> about it.
When I think the usecase for zram-swap, it is used for small memory
but not sure because these days, mobile phone DRAM size tend to be
big(ex, 3G) and they want to use zRAM for swap due to wear-leveling
of nand. When I consier the trend, they might set zram-swap to about
500M in future. In that case, 1% is 5M and given zram comp ratio(ie,
max 5:1), it could be 25M which is never small for the application.
So, IMO, we need more fine-grained knob.
>
> If yes then we should do something. I don't like the "bytes" thing
> much because it requires that the operator know the pool size
> beforehand, and any time that changes, the "bytes" needs hanging too.
> Ratios are nice but percent is too coarse. Maybe kernel should start
> using "ppm" for ratios, parts per million. hrm.
Okay, I will consider it more in next spin.
>
> > > > @@ -711,6 +732,7 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
> > > > down_write(&zram->init_lock);
> > > >
> > > > zram->limit_pages = 0;
> > > > + atomic_set(&zram->alloc_fail, 0);
> > > >
> > > > if (!init_done(zram)) {
> > > > up_write(&zram->init_lock);
> > > > @@ -944,6 +966,34 @@ static int zram_slot_free_notify(struct block_device *bdev,
> > > > return 0;
> > > > }
> > > >
> > > > +static int zram_full(struct block_device *bdev, void *arg)
> > >
> > > This could return a bool. That implies that zram_swap_hint should
> > > return bool too, but as we haven't been told what the zram_swap_hint
> > > return value does, I'm a bit stumped.
> >
> > Hmm, currently, SWAP_FREE doesn't use return and SWAP_FULL uses return
> > as bool so in the end, we can change it as bool but I want to remain it
> > as int for the future. At least, we might use it as propagating error
> > in future. Instead, I will use *arg to return the result instead of
> > return val. But I'm not strong so if you want to remove return val,
> > I will do it. For clarifictaion, please tell me again if you want.
>
> I'm easy, as long as it makes sense, is understandable by people other
> than he-who-wrote-it and doesn't use argument names such as "arg".
Yeb.
--
Kind regards,
Minchan Kim
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2014-09-24 7:56 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-22 0:03 [PATCH v1 0/5] stop anon reclaim when zram is full Minchan Kim
2014-09-22 0:03 ` [PATCH v1 1/5] zram: generalize swap_slot_free_notify Minchan Kim
2014-09-22 20:41 ` Andrew Morton
2014-09-23 4:45 ` Minchan Kim
2014-09-22 0:03 ` [PATCH v1 2/5] mm: add full variable in swap_info_struct Minchan Kim
2014-09-22 20:45 ` Andrew Morton
2014-09-23 4:45 ` Minchan Kim
2014-09-24 2:53 ` Dan Streetman
2014-09-24 7:57 ` Minchan Kim
2014-09-22 0:03 ` [PATCH v1 3/5] mm: VM can be aware of zram fullness Minchan Kim
2014-09-24 14:12 ` Dan Streetman
2014-09-25 1:06 ` Minchan Kim
2014-09-25 1:31 ` Dan Streetman
2014-09-22 0:03 ` [PATCH v1 4/5] zram: add swap full hint Minchan Kim
2014-09-22 21:11 ` Andrew Morton
2014-09-23 4:56 ` Minchan Kim
2014-09-23 21:17 ` Andrew Morton
2014-09-24 7:57 ` Minchan Kim [this message]
2014-09-24 15:10 ` Jerome Marchand
2014-09-25 1:07 ` Minchan Kim
2014-09-24 14:01 ` Dan Streetman
2014-09-25 1:02 ` Minchan Kim
2014-09-25 15:52 ` Dan Streetman
2014-10-06 23:36 ` Minchan Kim
2014-10-06 23:46 ` Minchan Kim
2014-10-08 18:29 ` Dan Streetman
2014-09-22 0:03 ` [PATCH v1 5/5] zram: add fullness knob to control swap full Minchan Kim
2014-09-22 21:17 ` Andrew Morton
2014-09-23 4:57 ` Minchan Kim
2014-12-02 3:04 ` [PATCH v1 0/5] stop anon reclaim when zram is full Minchan Kim
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140924075712.GA3181@bbox \
--to=minchan@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=ddstreet@ieee.org \
--cc=hughd@google.com \
--cc=jmarchan@redhat.com \
--cc=juno.choi@lge.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=ngupta@vflare.org \
--cc=semenzato@google.com \
--cc=sergey.senozhatsky@gmail.com \
--cc=shli@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).