LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Minchan Kim <minchan@kernel.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com
Subject: Re: [PATCH 4/4] mm: zswap: add basic meminfo and vmstat coverage
Date: Wed, 10 Nov 2021 11:11:26 -0800	[thread overview]
Message-ID: <YYwZXrL3Fu8/vLZw@google.com> (raw)
In-Reply-To: <YYFT6VtNT1Fvl4Iz@cmpxchg.org>

Hi Johannes,

On Tue, Nov 02, 2021 at 11:06:17AM -0400, Johannes Weiner wrote:
> Hi Minchan,
> 
> Sorry about the delay, I'm just now getting back to these patches.
> 
> On Mon, Aug 30, 2021 at 11:49:59AM -0700, Minchan Kim wrote:
> > Hi Johannes,
> > 
> > On Thu, Aug 19, 2021 at 03:55:33PM -0400, Johannes Weiner wrote:
> > > Currently it requires poking at debugfs to figure out the size of the
> > > zswap cache size on a host. There are no counters for reads and writes
> > > against the cache. This makes it difficult to understand behavior on
> > > production systems.
> > > 
> > > Print zswap memory consumption in /proc/meminfo, count zswapouts and
> > > zswapins in /proc/vmstat.
> > > 
> > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> > > ---
> > >  fs/proc/meminfo.c             |  4 ++++
> > >  include/linux/swap.h          |  4 ++++
> > >  include/linux/vm_event_item.h |  4 ++++
> > >  mm/vmstat.c                   |  4 ++++
> > >  mm/zswap.c                    | 11 +++++------
> > >  5 files changed, 21 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> > > index 6fa761c9cc78..2dc474940691 100644
> > > --- a/fs/proc/meminfo.c
> > > +++ b/fs/proc/meminfo.c
> > > @@ -86,6 +86,10 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
> > >  
> > >  	show_val_kb(m, "SwapTotal:      ", i.totalswap);
> > >  	show_val_kb(m, "SwapFree:       ", i.freeswap);
> > > +#ifdef CONFIG_ZSWAP
> > > +	seq_printf(m,  "Zswap:          %8lu kB\n",
> > > +		   (unsigned long)(zswap_pool_total_size >> 10));
> > 
> > Since we have zram as well as zswap, it would be great if
> > we can abstract both at once without introducing another
> > "Zram: " stuff in meminfo. A note: zram can support fs based on
> > on zram blk device as well as swap. Thus, term would be better
> > to say "compressed" rather than "swap".
> > 
> > How about this?
> > 
> > "Compressed: xx kB"
> 
> Wouldn't it make more sense to keep separate counters? Zswap and zram
> are quite different from each other.
> 
> From an MM perspective, zram is an opaque storage backend. zswap OTOH
> is an explicit MM cache stage which may in the future make different
> decisions than zram, be integrated into vmscan's LRU hierarchy
> etc. And in theory, you could put zswap with fast compression in front
> of a zram device with denser compression, right?

My view is the the allocators aims to store compressed memory.
Likewise slab allocator, we could use the allocator any places
and display the total memory usage from the allocator in meminfo
instead of each subsystem and look at slabinfo if we need further
break down. I think it could work for this case, too.

> 
> I agree zram should probably also have memory counters, but I think it
> makes sense to recognize zswap as a unique MM layer.

Under your view, I think it would introduce Zram-swap, Zram-block
as well as Zswap. If folks think it's better idea, I am fine and
happy to post a patch to merge it along with this patch.

  reply	other threads:[~2021-11-10 19:11 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-19 19:55 [PATCH 1/4] mm: Kconfig: move swap and slab config options to the MM section Johannes Weiner
2021-08-19 19:55 ` [PATCH 2/4] mm: Kconfig: group swap, slab, hotplug and thp options into submenus Johannes Weiner
2021-08-24 12:03   ` Vlastimil Babka
2021-08-24 14:56     ` Johannes Weiner
2021-08-19 19:55 ` [PATCH 3/4] mm: Kconfig: simplify zswap configuration Johannes Weiner
2021-08-24 12:04   ` Vlastimil Babka
2021-08-19 19:55 ` [PATCH 4/4] mm: zswap: add basic meminfo and vmstat coverage Johannes Weiner
2021-08-24 12:05   ` Vlastimil Babka
2021-08-30 18:04   ` kernel test robot
2021-08-30 18:49   ` Minchan Kim
2021-11-02 15:06     ` Johannes Weiner
2021-11-10 19:11       ` Minchan Kim [this message]
2021-08-24 11:47 ` [PATCH 1/4] mm: Kconfig: move swap and slab config options to the MM section Vlastimil Babka

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=YYwZXrL3Fu8/vLZw@google.com \
    --to=minchan@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=hannes@cmpxchg.org \
    --cc=kernel-team@fb.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --subject='Re: [PATCH 4/4] mm: zswap: add basic meminfo and vmstat coverage' \
    /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

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).