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From: Zhaoyang Huang <huangzhaoyang@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
	Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
	"open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Nitin Gupta <ngupta@vflare.org>
Subject: Re: [PATCH] driver: zram: fix wrong counting on pages_store
Date: Tue, 27 Jul 2021 13:45:04 +0800	[thread overview]
Message-ID: <CAGWkznGt9hWGM4KF-0WX4noe=piB4==T4cVuSETDGAsn7Xgi=Q@mail.gmail.com> (raw)
In-Reply-To: <CAGWkznFifWQSMAoz-qD2M_qnZL=qi8XsJPVxet6Cbt_euD4eAg@mail.gmail.com>

On Tue, Jul 27, 2021 at 9:32 AM Zhaoyang Huang <huangzhaoyang@gmail.com> wrote:
>
> On Tue, Jul 27, 2021 at 1:53 AM Minchan Kim <minchan@kernel.org> wrote:
> >
> > On Mon, Jul 26, 2021 at 10:27:40AM +0900, Sergey Senozhatsky wrote:
> > > On (21/07/20 14:47), Huangzhaoyang wrote:
> > > > It makes the statistic confused when counting pages_store in during writeback.
> > > > pages_store should just reflect the swapped pages on ZRAM, while bd_writes be
> > > > responsible for writeback things.
> > > >
> > > > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > > > ---
> > > >  drivers/block/zram/zram_drv.c | 1 -
> > > >  1 file changed, 1 deletion(-)
> > > >
> > > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > > > index cf8deec..6bdaa9d 100644
> > > > --- a/drivers/block/zram/zram_drv.c
> > > > +++ b/drivers/block/zram/zram_drv.c
> > > > @@ -765,7 +765,6 @@ static ssize_t writeback_store(struct device *dev,
> > > >             zram_set_flag(zram, index, ZRAM_WB);
> > > >             zram_set_element(zram, index, blk_idx);
> > > >             blk_idx = 0;
> > > > -           atomic64_inc(&zram->stats.pages_stored);
> > >
> > > Yeah, I think we don't need it here.
> > >
> > > Minchan, what do you think?
> >
> > What pages_stored currently represents is orig_data_size from mm_stat
> >
> >  ================ =============================================================
> >  orig_data_size   uncompressed size of data stored in this disk.
> >                   Unit: bytes
> >
> > Thus, if we don't increase it after zram_free_page, it loses what's
> > the original data size which would be important to calculate
> > compression ratio along with compr_data_size.
> zram_free_page??  What the commit try to fix is pages_stored being
> increased incorrectly in writeback_store, which will lead to wrong
> statistic on orig size of ZRAM.
OK, if I understand right, I think what you mean is the page count
corresponding to SWAP should be still available even if it is written
back to the backing dev.So we need to increase page_stored again after
zram_free_page free it.

      reply	other threads:[~2021-07-27  5:45 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-20  6:47 Huangzhaoyang
2021-07-25  1:19 ` [Resend PATCH] " Zhaoyang Huang
2021-07-26  1:27 ` [PATCH] " Sergey Senozhatsky
2021-07-26 17:53   ` Minchan Kim
2021-07-27  1:32     ` Zhaoyang Huang
2021-07-27  5:45       ` Zhaoyang Huang [this message]

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