On 10/21/2014 09:27 AM, karam....@lge.com wrote:
> From: "karam.lee" <karam....@lge.com>
>
> 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....@lge.com>
> ---
> 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..696f0b5 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 = 1;
Small nitpick, but why do you initialize ret to 1? It doesn't seem to be
ever used (nor is 1 a valid return value AFAICT).
It otherwise looks good.
Acked-by: Jerome Marchand <jmarc...@redhat.com>
> + 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;
> + goto out_unlock;
> + }
> +
> + index = sector >> SECTORS_PER_PAGE_SHIFT;
> + offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT;
> +
> + bv.bv_page = page;
> + bv.bv_len = PAGE_SIZE;
> + bv.bv_offset = 0;
> +
> + ret = zram_bvec_rw(zram, &bv, index, offset, rw);
> +
> +out_unlock:
> + up_read(&zram->init_lock);
> +out:
> + page_endio(page, rw, ret);
> + return ret;
> +}
> +
> static const struct block_device_operations zram_devops = {
> .swap_slot_free_notify = zram_slot_free_notify,
> + .rw_page = zram_rw_page,
> .owner = THIS_MODULE
> };
>
>
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