From mboxrd@z Thu Jan 1 00:00:00 1970 From: Minchan Kim Subject: Re: [PATCH 4/5] mm: zswap: add basic meminfo and vmstat coverage Date: Thu, 28 Apr 2022 09:59:53 -0700 Message-ID: References: <20220427160016.144237-1-hannes@cmpxchg.org> <20220427160016.144237-5-hannes@cmpxchg.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=ZDYp2Y77Y0buY8pwqMtyLcOAE+45dX/zsVX064x7LX0=; b=T5FFCS6UotdYG74iCBtYERNBWBj0bDr3newq9MZ2CU9iAU7Mvp0pkO5CiXjERw7Z4h dtH/fRg2OWCurCYY/v6eAgs86zEARY/k+6a8gV+KFp5cnuwhIc+5wD3LrAQy89ZpYjGn zh4XBjGCMww1+wmz3wu4aESExAsU5U3STiPkEsu5tnyY86NbVyZRjEGc1jDnJahB9RoI akO6N05QtWT7jO5Nq0Op+bDPxkkBcZqWYPxqRyT/l6r+xlIU6CgdduGLX8sp2gwYd8TJ 5Y4/YsTIot25E8QLmvce9ubCcCd/jkHViC+wf9ZWxyci0PT7D76bJhMzp9dpPEi16tdZ /xvQ== Sender: Minchan Kim Content-Disposition: inline In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: Andrew Morton , Michal Hocko , Roman Gushchin , Shakeel Butt , Seth Jennings , Dan Streetman , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com On Thu, Apr 28, 2022 at 10:25:59AM -0400, Johannes Weiner wrote: > On Wed, Apr 27, 2022 at 03:16:48PM -0700, Minchan Kim wrote: > > On Wed, Apr 27, 2022 at 05:20:29PM -0400, Johannes Weiner wrote: > > > On Wed, Apr 27, 2022 at 01:29:34PM -0700, Minchan Kim wrote: > > > > Hi Johannes, > > > > > > > > On Wed, Apr 27, 2022 at 12:00:15PM -0400, Johannes Weiner wrote: > > > > > Currently it requires poking at debugfs to figure out the size and > > > > > population of the zswap cache on a host. There are no counters for > > > > > reads and writes against the cache. As a result, it's difficult to > > > > > understand zswap behavior on production systems. > > > > > > > > > > Print zswap memory consumption and how many pages are zswapped out in > > > > > /proc/meminfo. Count zswapouts and zswapins in /proc/vmstat. > > > > > > > > > > Signed-off-by: Johannes Weiner > > > > > --- > > > > > fs/proc/meminfo.c | 7 +++++++ > > > > > include/linux/swap.h | 5 +++++ > > > > > include/linux/vm_event_item.h | 4 ++++ > > > > > mm/vmstat.c | 4 ++++ > > > > > mm/zswap.c | 13 ++++++------- > > > > > 5 files changed, 26 insertions(+), 7 deletions(-) > > > > > > > > > > diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c > > > > > index 6fa761c9cc78..6e89f0e2fd20 100644 > > > > > --- a/fs/proc/meminfo.c > > > > > +++ b/fs/proc/meminfo.c > > > > > @@ -86,6 +86,13 @@ 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)); > > > > > + seq_printf(m, "Zswapped: %8lu kB\n", > > > > > + (unsigned long)atomic_read(&zswap_stored_pages) << > > > > > + (PAGE_SHIFT - 10)); > > > > > +#endif > > > > > > > > I agree it would be very handy to have the memory consumption in meminfo > > > > > > > > https://lore.kernel.org/all/YYwZXrL3Fu8%2FvLZw@google.com/ > > > > > > > > If we really go this Zswap only metric instead of general term > > > > "Compressed", I'd like to post maybe "Zram:" with same reason > > > > in this patchset. Do you think that's better idea instead of > > > > introducing general term like "Compressed:" or something else? > > > > > > I'm fine with changing it to Compressed. If somebody cares about a > > > more detailed breakdown, we can add Zswap, Zram subsets as needed. > > > > Thanks! Please consider ZSWPIN to rename more general term, too. > > That doesn't make sense to me. > > Zram is a swap backend, its traffic is accounted in PSWPIN/OUT. Zswap > is a writeback cache on top of the swap backend. It has pages > entering, refaulting, and being written back to the swap backend > (PSWPOUT). A zswpout and a zramout are different things. Think about that system has two swap devices (storage + zram). I think it's useful to know how many swap IO comes from zram and rest of them are storage.