Re: [PATCH 4/5] mm: zswap: add basic meminfo and vmstat coverage

Minchan Kim
2022-04-27T20:29:34Z

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 <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
> ---
> 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-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org/

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?