From 8c7f01025f7becd577bed9af93f974fc6798c5a3 Mon Sep 17 00:00:00 2001 From: "karam.lee" Date: Fri, 12 Dec 2014 16:56:53 -0800 Subject: [PATCH] zram: implement rw_page operation of zram 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. 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%. [minchan@kernel.org: make rw_page opeartion return 0] [minchan@kernel.org: rely on the bi_end_io for zram_rw_page fails] [sergey.senozhatsky@gmail.com: code cleanup] [minchan@kernel.org: add comment] Signed-off-by: karam.lee Acked-by: Minchan Kim Acked-by: Jerome Marchand Cc: Matthew Wilcox Cc: Nitin Gupta Cc: Signed-off-by: Minchan Kim Signed-off-by: Sergey Senozhatsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/block/zram/zram_drv.c | 44 +++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 98af4aae2618..976eab6f35b9 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -945,8 +945,52 @@ 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, err; + 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); + return -EINVAL; + } + + down_read(&zram->init_lock); + if (unlikely(!init_done(zram))) { + err = -EIO; + 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; + + err = zram_bvec_rw(zram, &bv, index, offset, rw); +out_unlock: + up_read(&zram->init_lock); + /* + * If I/O fails, just return error(ie, non-zero) without + * calling page_endio. + * It causes resubmit the I/O with bio request by upper functions + * of rw_page(e.g., swap_readpage, __swap_writepage) and + * bio->bi_end_io does things to handle the error + * (e.g., SetPageError, set_page_dirty and extra works). + */ + if (err == 0) + page_endio(page, rw, 0); + return err; +} + static const struct block_device_operations zram_devops = { .swap_slot_free_notify = zram_slot_free_notify, + .rw_page = zram_rw_page, .owner = THIS_MODULE };