From: Shakeel Butt <shakeelb@google.com>
To: Johannes Weiner <hannes@cmpxchg.org>,
Yosry Ahmed <yosryahmed@google.com>,
Yuanchu Xie <yuanchu@google.com>
Cc: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>, Roman Gushchin <guro@fb.com>,
Seth Jennings <sjenning@redhat.com>,
Dan Streetman <ddstreet@ieee.org>, Linux MM <linux-mm@kvack.org>,
Cgroups <cgroups@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH 4/5] mm: zswap: add basic meminfo and vmstat coverage
Date: Thu, 5 May 2022 12:30:29 -0700 [thread overview]
Message-ID: <CALvZod7_5CNjMqEo_SseW7VoVW9gRC8ZoVy=f9SAOL4+-1jR4A@mail.gmail.com> (raw)
In-Reply-To: <Ymqv25+8IX2wqKzu@cmpxchg.org>
+Yosry & Yuanchu
On Thu, Apr 28, 2022 at 8:17 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
[...]
> >
> > Yes, we have some modifications to zswap to make it work without any
> > backing real swap.
>
> Not sure if you can share them, but I would be interested in those
> changes. We have real backing swap, but because of the way swap
> entries are allocated, pages stored in zswap will consume physical
> disk slots. So on top of regular swap, you need to provision disk
> space for zswap as well, which is unfortunate.
>
> What could be useful is a separate swap entry address space that maps
> zswap slots and disk slots alike. This would fix the above problem. It
> would have the added benefit of making swapoff much simpler and faster
> too, as it doesn't need to chase down page tables to free disk slots.
>
I think we can share the code. Adding Yosry & Yuanchu who are
currently maintaining that piece of code.
Though that code might not be in an upstreamable state. At the high
level, it introduces a new type of swap (SWP_GHOST) which underlying
is a truncated file, so no real disk space is needed. The zswap always
accepts the page, so the kernel never tries to go to the underlying
swapfile (reality is a bit more complicated due to the presence of
incompressible memory and no real disk present on the system).
next prev parent reply other threads:[~2022-05-05 19:30 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-27 16:00 [PATCH 0/5] zswap: cgroup accounting & control Johannes Weiner
2022-04-27 16:00 ` [PATCH 1/5] mm: Kconfig: move swap and slab config options to the MM section Johannes Weiner
2022-04-27 16:00 ` [PATCH 2/5] mm: Kconfig: group swap, slab, hotplug and thp options into submenus Johannes Weiner
2022-04-27 16:00 ` [PATCH 3/5] mm: Kconfig: simplify zswap configuration Johannes Weiner
2022-04-27 16:00 ` [PATCH 4/5] mm: zswap: add basic meminfo and vmstat coverage Johannes Weiner
2022-04-27 18:36 ` Andrew Morton
2022-04-27 18:53 ` Johannes Weiner
2022-04-27 19:50 ` Johannes Weiner
2022-04-27 19:51 ` Johannes Weiner
2022-04-27 20:29 ` Minchan Kim
2022-04-27 21:20 ` Johannes Weiner
2022-04-27 21:36 ` Johannes Weiner
2022-04-27 22:12 ` Minchan Kim
2022-04-28 14:05 ` Johannes Weiner
2022-04-28 17:02 ` Minchan Kim
2022-04-28 17:27 ` Johannes Weiner
2022-04-27 23:36 ` Shakeel Butt
2022-04-28 14:36 ` Johannes Weiner
2022-04-28 14:49 ` Shakeel Butt
2022-04-28 15:16 ` Johannes Weiner
2022-04-28 16:59 ` Yang Shi
2022-05-05 19:30 ` Shakeel Butt [this message]
2022-04-28 16:54 ` Yang Shi
2022-05-05 19:33 ` Shakeel Butt
2022-05-05 22:24 ` Suleiman Souhlal
2022-05-05 23:54 ` Yu Zhao
2022-04-27 22:16 ` Minchan Kim
2022-04-28 14:25 ` Johannes Weiner
2022-04-28 16:59 ` Minchan Kim
2022-04-28 17:23 ` Johannes Weiner
2022-04-28 17:31 ` Minchan Kim
2022-04-28 18:34 ` Johannes Weiner
2022-04-28 19:58 ` Minchan Kim
2022-04-27 16:00 ` [PATCH 5/5] zswap: memcg accounting Johannes Weiner
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