From: "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>
To: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Shakeel Butt <shakeelb@google.com>,
Minchan Kim <minchan@kernel.org>,
"Mike Galbraith" <efault@gmx.de>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
NitinGupta <ngupta@vflare.org>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
"tiantao (H)" <tiantao6@hisilicon.com>
Subject: RE: [PATCH] zsmalloc: do not use bit_spin_lock
Date: Tue, 22 Dec 2020 21:06:35 +0000 [thread overview]
Message-ID: <1d0d4a3576e74d128d7849342a7e9faf@hisilicon.com> (raw)
In-Reply-To: <CAM4kBBJjCYX0DQZ8de9LsFV6L+eF4tZe-NN=jiAz9WLWYrsCsQ@mail.gmail.com>
> -----Original Message-----
> From: Vitaly Wool [mailto:vitaly.wool@konsulko.com]
> Sent: Tuesday, December 22, 2020 10:44 PM
> To: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com>
> Cc: Shakeel Butt <shakeelb@google.com>; Minchan Kim <minchan@kernel.org>; Mike
> Galbraith <efault@gmx.de>; LKML <linux-kernel@vger.kernel.org>; linux-mm
> <linux-mm@kvack.org>; Sebastian Andrzej Siewior <bigeasy@linutronix.de>;
> NitinGupta <ngupta@vflare.org>; Sergey Senozhatsky
> <sergey.senozhatsky.work@gmail.com>; Andrew Morton
> <akpm@linux-foundation.org>; tiantao (H) <tiantao6@hisilicon.com>
> Subject: Re: [PATCH] zsmalloc: do not use bit_spin_lock
>
> On Tue, 22 Dec 2020, 03:11 Song Bao Hua (Barry Song),
> <song.bao.hua@hisilicon.com> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Song Bao Hua (Barry Song)
> > > Sent: Tuesday, December 22, 2020 3:03 PM
> > > To: 'Vitaly Wool' <vitaly.wool@konsulko.com>
> > > Cc: Shakeel Butt <shakeelb@google.com>; Minchan Kim <minchan@kernel.org>;
> Mike
> > > Galbraith <efault@gmx.de>; LKML <linux-kernel@vger.kernel.org>; linux-mm
> > > <linux-mm@kvack.org>; Sebastian Andrzej Siewior <bigeasy@linutronix.de>;
> > > NitinGupta <ngupta@vflare.org>; Sergey Senozhatsky
> > > <sergey.senozhatsky.work@gmail.com>; Andrew Morton
> > > <akpm@linux-foundation.org>; tiantao (H) <tiantao6@hisilicon.com>
> > > Subject: RE: [PATCH] zsmalloc: do not use bit_spin_lock
> > >
> > >
> > > > I'm still not convinced. Will kmap what, src? At this point src might
> become
> > > just a bogus pointer.
> > >
> > > As long as the memory is still there, we can kmap it by its page struct.
> But
> > > if
> > > it is not there anymore, we have no way.
> > >
> > > > Why couldn't the object have been moved somewhere else (due to the compaction
> > > mechanism for instance)
> > > > at the time DMA kicks in?
> > >
> > > So zs_map_object() will guarantee the src won't be moved by holding those
> > > preemption-disabled lock?
> > > If so, it seems we have to drop the MOVABLE gfp in zswap for zsmalloc case?
> > >
> >
> > Or we can do get_page() to avoid the movement of the page.
>
>
> I would like to discuss this more in zswap context than zsmalloc's.
> Since zsmalloc does not implement reclaim callback, using it in zswap
> is a corner case anyway.
I see. But it seems we still need a solution for the compatibility
of zsmalloc and zswap? this will require change in either zsmalloc
or zswap.
or do you want to make zswap depend on !ZSMALLOC?
>
> zswap, on the other hand, may be dealing with some new backends in
> future which have more chances to become mainstream. Imagine typical
> NUMA-like cases, i. e. a zswap pool allocated in some kind SRAM, or in
> unused video memory. In such a case if you try to use a pointer to an
> invalidated zpool mapping, you are on the way to thrash the system.
> So: no assumptions that the zswap pool is in regular linear RAM should
> be made.
>
> ~Vitaly
Thanks
Barry
next prev parent reply other threads:[~2020-12-22 21:06 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-19 10:04 [patch] zswap: fix zswap_frontswap_load() vs zsmalloc::map/unmap() might_sleep() splat Mike Galbraith
2020-12-19 10:12 ` Mike Galbraith
2020-12-19 10:20 ` Vitaly Wool
2020-12-19 10:27 ` Mike Galbraith
2020-12-19 10:46 ` Vitaly Wool
2020-12-19 10:59 ` Mike Galbraith
2020-12-19 11:03 ` Mike Galbraith
2020-12-20 0:22 ` [PATCH] zsmalloc: do not use bit_spin_lock Vitaly Wool
2020-12-20 1:18 ` Matthew Wilcox
2020-12-20 7:21 ` Vitaly Wool
2021-01-14 16:17 ` Sebastian Andrzej Siewior
2020-12-20 1:23 ` Mike Galbraith
2020-12-20 4:11 ` Mike Galbraith
2020-12-20 7:47 ` Mike Galbraith
2020-12-20 21:20 ` Song Bao Hua (Barry Song)
2020-12-20 22:10 ` Mike Galbraith
2020-12-20 1:56 ` Mike Galbraith
2020-12-21 17:24 ` Minchan Kim
2020-12-21 19:20 ` Vitaly Wool
2020-12-21 19:50 ` Shakeel Butt
2020-12-21 20:05 ` Song Bao Hua (Barry Song)
2020-12-21 21:02 ` Shakeel Butt
2020-12-21 21:25 ` Song Bao Hua (Barry Song)
2020-12-21 22:11 ` Vitaly Wool
2020-12-21 22:42 ` Song Bao Hua (Barry Song)
2020-12-21 23:35 ` Song Bao Hua (Barry Song)
2020-12-22 0:59 ` Vitaly Wool
2020-12-22 1:10 ` Song Bao Hua (Barry Song)
2020-12-22 1:42 ` Song Bao Hua (Barry Song)
2020-12-22 1:57 ` Vitaly Wool
2020-12-22 2:07 ` Song Bao Hua (Barry Song)
2020-12-22 2:10 ` Song Bao Hua (Barry Song)
2020-12-22 9:44 ` Vitaly Wool
2020-12-22 21:06 ` Song Bao Hua (Barry Song) [this message]
2020-12-23 0:11 ` Vitaly Wool
2020-12-23 12:44 ` tiantao (H)
2020-12-23 18:25 ` Vitaly Wool
2021-01-14 16:18 ` Sebastian Andrzej Siewior
2021-01-14 16:29 ` Vitaly Wool
2021-01-14 16:56 ` Sebastian Andrzej Siewior
2021-01-14 17:15 ` Vitaly Wool
2021-01-14 17:18 ` Sebastian Andrzej Siewior
2020-12-21 22:46 ` Shakeel Butt
2020-12-21 23:02 ` Song Bao Hua (Barry Song)
2020-12-22 9:20 ` David Laight
2020-12-22 9:32 ` Vitaly Wool
2020-12-21 20:22 ` 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=1d0d4a3576e74d128d7849342a7e9faf@hisilicon.com \
--to=song.bao.hua@hisilicon.com \
--cc=akpm@linux-foundation.org \
--cc=bigeasy@linutronix.de \
--cc=efault@gmx.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=minchan@kernel.org \
--cc=ngupta@vflare.org \
--cc=sergey.senozhatsky.work@gmail.com \
--cc=shakeelb@google.com \
--cc=tiantao6@hisilicon.com \
--cc=vitaly.wool@konsulko.com \
/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