Hello Minchan,
On (09/12/14 08:21), Minchan Kim wrote:
> Hey Sergey,
>
> Sorry for late review.
>
> On Fri, Sep 05, 2014 at 09:57:09PM +0900, Sergey Senozhatsky wrote:
> > notify_free device attribute accounts the number of slot free notifications
> > and internally represents the number of zram_free_page() calls. Slot free
> > notifications are sent only when device is used as a swap device, hence
> > notify_free is used only for swap devices. Since f4659d8e620d08 (zram:
> > support REQ_DISCARD) ZRAM handles yet another one free notification (also
> > via zram_free_page() call) -- REQ_DISCARD requests, which are sent by a
> > filesystem, whenever some data blocks are discarded. However, there is no
> > way to know the number of notifications in the latter case.
> >
> > Use notify_free to account the number of pages freed in zram_free_page(),
> > instead of accounting only swap_slot_free_notify() calls (each
> > zram_slot_free_notify() call frees one page).
> >
> > This means that depending on usage scenario notify_free represents:
> > a) the number of pages freed because of slot free notifications, which is
> > equal to the number of swap_slot_free_notify() calls, so there is no
> > behaviour change
> >
> > b) the number of pages freed because of REQ_DISCARD notifications
> >
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhat...@gmail.com>
> > ---
> > Documentation/ABI/testing/sysfs-block-zram | 13 ++++++++-----
> > drivers/block/zram/zram_drv.c | 2 +-
> > 2 files changed, 9 insertions(+), 6 deletions(-)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-block-zram
> > b/Documentation/ABI/testing/sysfs-block-zram
> > index b13dc99..a6148ea 100644
> > --- a/Documentation/ABI/testing/sysfs-block-zram
> > +++ b/Documentation/ABI/testing/sysfs-block-zram
> > @@ -77,11 +77,14 @@ What: /sys/block/zram<id>/notify_free
> > Date: August 2010
> > Contact: Nitin Gupta <ngu...@vflare.org>
> > Description:
> > - The notify_free file is read-only and specifies the number of
> > - swap slot free notifications received by this device. These
> > - notifications are sent to a swap block device when a swap slot
> > - is freed. This statistic is applicable only when this disk is
> > - being used as a swap disk.
> > + The notify_free file is read-only. Depending on device usage
> > + scenario it may account a) the number of pages freed because
> > + of swap slot free notifications or b) the number of pages freed
> > + because of REQ_DISCARD requests sent by bio. The former ones
> > + are sent to a swap block device when a swap slot is freed, which
> > + implies that this disk is being used as a swap disk. The latter
> > + ones are sent by filesystem mounted with discard option,
> > + whenever some data blocks are getting discarded.
> >
> > What: /sys/block/zram<id>/zero_pages
> > Date: August 2010
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index d78b245..bc20fe1 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -410,6 +410,7 @@ static void zram_free_page(struct zram *zram, size_t
> > index)
> > atomic64_sub(zram_get_obj_size(meta, index),
> > &zram->stats.compr_data_size);
> > atomic64_dec(&zram->stats.pages_stored);
> > + atomic64_inc(&zram->stats.notify_free);
>
> It is wrong. The zram_free_page is called at several places and
> they are all not notify free.
> Pz, account it in zram_slot_free_notify and zram_bio_discard.
wow, why did I do that... good catch!
will resend shortly.
sorry.
-ss
> >
> > meta->table[index].handle = 0;
> > zram_set_obj_size(meta, index, 0);
> > @@ -938,7 +939,6 @@ static void zram_slot_free_notify(struct block_device
> > *bdev,
> > bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
> > zram_free_page(zram, index);
> > bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> > - atomic64_inc(&zram->stats.notify_free);
> > }
> >
> > static const struct block_device_operations zram_devops = {
> > --
> > 2.1.0.134.gb1ae451
> >
> > --
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>
> --
> Kind regards,
> Minchan Kim
>
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