Re: [PATCH v4 3/3] zram: implement rw_page operation of zram

From: Minchan Kim
Date: Wed Oct 22 2014 - 03:26:47 EST


Hi karam,

On Wed, Oct 22, 2014 at 04:04:14PM +0900, karam.lee@xxxxxxx wrote:
> From: "karam.lee" <karam.lee@xxxxxxx>
>
> This patch implements rw_page operation for zram block device.
>
> I implemented the feature in zram and tested it.
> Test bed was the G2, LG electronic mobile device, whtich has msm8974
> processor and 2GB memory.
> With a memory allocation test program consuming memory, the system
> generates swap.
> And operating time of swap_write_page() was measured.
>
> --------------------------------------------------
> | | operating time | improvement |
> | | (20 runs average) | |
> --------------------------------------------------
> |with patch | 1061.15 us | +2.4% |
> --------------------------------------------------
> |without patch| 1087.35 us | |
> --------------------------------------------------
>
> Each test(with paged_io,with BIO) result set shows normal distribution
> and has equal variance.
> I mean the two values are valid result to compare.
> I can say operation with paged I/O(without BIO) is faster 2.4% with
> confidence level 95%.
>
> Signed-off-by: karam.lee <karam.lee@xxxxxxx>
> ---
> drivers/block/zram/zram_drv.c | 38 ++++++++++++++++++++++++++++++++++++++
> 1 file changed, 38 insertions(+)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 4565fdc..8bbd4f2 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -810,8 +810,46 @@ static void zram_slot_free_notify(struct block_device *bdev,
> atomic64_inc(&zram->stats.notify_free);
> }
>
> +static int zram_rw_page(struct block_device *bdev, sector_t sector,
> + struct page *page, int rw)
> +{
> + int offset, ret;
> + u32 index;
> + struct zram *zram;
> + struct bio_vec bv;
> +
> + zram = bdev->bd_disk->private_data;
> + if (!valid_io_request(zram, sector, PAGE_SIZE)) {
> + atomic64_inc(&zram->stats.invalid_io);
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + down_read(&zram->init_lock);
> + if (unlikely(!init_done(zram))) {
> + ret = -ENOMEM;

Why is it -ENOMEM?
I think EIO is better like bio_io_error.

--
Kind regards,
Minchan Kim
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