Commit 0d31c7c2 authored by Denis V. Lunev's avatar Denis V. Lunev Committed by Stefan Hajnoczi
Browse files

block/parallels: delay writing to BAT till bdrv_co_flush_to_os 



The idea is that we do not need to immediately sync BAT to the image as
from the guest point of view there is a possibility that IO is lost
even in the physical controller until flush command was finished.
bdrv_co_flush_to_os is exactly the right place for this purpose.

Technically the patch uses loaded BAT data as a cache and performs
actual on-disk metadata updates in parallels_co_flush_to_os callback.

This patch speed ups
  qemu-img create -f parallels -o cluster_size=64k ./1.hds 64G
  qemu-io -f parallels -c "write -P 0x11 0 1024k" 1.hds
writing from 50-60 Mb/sec to 80-90 Mb/sec on rotational media and
from 160 Mb/sec to 190 Mb/sec on SSD disk.

Signed-off-by: default avatarDenis V. Lunev <den@openvz.org>
Reviewed-by: default avatarRoman Kagan <rkagan@parallels.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarRoman Kagan <rkagan@parallels.com>
Message-id: 1430207220-24458-25-git-send-email-den@openvz.org
CC: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 2d68e22e

block/parallels.c

+44 −6
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ 
#include "qemu-common.h"

#include "block/block_int.h"

#include "qemu/module.h"

#include "qemu/bitmap.h"



/**************************************************************/
@@ -66,6 +67,9 @@ typedef struct BDRVParallelsState { 
    uint32_t header_size;

    bool header_unclean;



    unsigned long *bat_dirty_bmap;

    unsigned int  bat_dirty_block;



    uint32_t *bat_bitmap;

    unsigned int bat_size;
@@ -165,14 +169,42 @@ static int64_t allocate_cluster(BlockDriverState *bs, int64_t sector_num) 
    }



    s->bat_bitmap[idx] = cpu_to_le32(pos / s->off_multiplier);

    ret = bdrv_pwrite(bs->file, bat_entry_off(idx), s->bat_bitmap + idx,

                      sizeof(s->bat_bitmap[idx]));



    bitmap_set(s->bat_dirty_bmap, bat_entry_off(idx) / s->bat_dirty_block, 1);

    return bat2sect(s, idx) + offset;

}





static coroutine_fn int parallels_co_flush_to_os(BlockDriverState *bs)

{

    BDRVParallelsState *s = bs->opaque;

    unsigned long size = DIV_ROUND_UP(s->header_size, s->bat_dirty_block);

    unsigned long bit;



    qemu_co_mutex_lock(&s->lock);



    bit = find_first_bit(s->bat_dirty_bmap, size);

    while (bit < size) {

        uint32_t off = bit * s->bat_dirty_block;

        uint32_t to_write = s->bat_dirty_block;

        int ret;



        if (off + to_write > s->header_size) {

            to_write = s->header_size - off;

        }

        ret = bdrv_pwrite(bs->file, off, (uint8_t *)s->header + off, to_write);

        if (ret < 0) {

        s->bat_bitmap[idx] = 0;

            qemu_co_mutex_unlock(&s->lock);

            return ret;

        }

    return bat2sect(s, idx) + offset;

        bit = find_next_bit(s->bat_dirty_bmap, size, bit + 1);

    }

    bitmap_zero(s->bat_dirty_bmap, size);



    qemu_co_mutex_unlock(&s->lock);

    return 0;

}





static int64_t coroutine_fn parallels_co_get_block_status(BlockDriverState *bs,

        int64_t sector_num, int nb_sectors, int *pnum)
@@ -557,6 +589,10 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags, 
        }

    }



    s->bat_dirty_block = 4 * getpagesize();

    s->bat_dirty_bmap =

        bitmap_new(DIV_ROUND_UP(s->header_size, s->bat_dirty_block));



    qemu_co_mutex_init(&s->lock);

    return 0;
@@ -578,6 +614,7 @@ static void parallels_close(BlockDriverState *bs) 
        parallels_update_header(bs);

    }



    g_free(s->bat_dirty_bmap);

    qemu_vfree(s->header);

}
@@ -608,6 +645,7 @@ static BlockDriver bdrv_parallels = { 
    .bdrv_close		= parallels_close,

    .bdrv_co_get_block_status = parallels_co_get_block_status,

    .bdrv_has_zero_init       = bdrv_has_zero_init_1,

    .bdrv_co_flush_to_os      = parallels_co_flush_to_os,

    .bdrv_co_readv  = parallels_co_readv,

    .bdrv_co_writev = parallels_co_writev,