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Re: [Qemu-devel] [PATCH] block/iscsi: precache the allocation status of
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] block/iscsi: precache the allocation status of a target |
Date: |
Thu, 30 Jun 2016 17:59:01 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 |
On 30/06/2016 13:08, Peter Lieven wrote:
> this fills up the allocationmap at iscsi_open. This helps
> to reduce the number of get_block_status requests during runtime
> significantly.
>
> Signed-off-by: Peter Lieven <address@hidden>
> ---
> block/iscsi.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/block/iscsi.c b/block/iscsi.c
> index 0cdcedb..04fb0a3 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -1774,6 +1774,22 @@ static int iscsi_open(BlockDriverState *bs, QDict
> *options, int flags,
> iscsilun->block_size) >>
> BDRV_SECTOR_BITS;
> if (iscsilun->lbprz) {
> ret = iscsi_allocmap_init(iscsilun, bs->open_flags);
> + if (ret == 0) {
> + unsigned int max_reqs = 64;
> + int64_t sector_num = 0;
> + while (max_reqs-- && sector_num < bs->total_sectors) {
> + int n;
> + BlockDriverState *file;
> + ret = bdrv_get_block_status(bs, sector_num,
> + BDRV_REQUEST_MAX_SECTORS,
> + &n, &file);
> + if (ret < 0) {
> + break;
> + }
> + sector_num += n;
> + ret = 0;
> + }
> + }
> }
> }
>
>
This can take a long time and the disks may not even be ever used. I
don't think it's a good idea.
Paolo