Re: [Qemu-devel] [PATCH v3] block/null: Latency simulation by adding new option "latency-ns"

[Kevin Wolf <kwolf@redhat.com>]

Am 11.03.2015 um 06:42 hat Fam Zheng geschrieben:
> Aio context switch should just work because the requests will be
> drained, so the scheduled timer(s) on the old context will be freed.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> 
> ---
> v3: latency_ns -> latency-ns; Add documentation in qapi json. [Eric]
> v2: Check for negative value; add sleep in null-co://. [Kevin]
> ---
>  block/null.c         | 55 +++++++++++++++++++++++++++++++++++++++++++++++-----
>  qapi/block-core.json |  5 ++++-
>  2 files changed, 54 insertions(+), 6 deletions(-)
> 
> diff --git a/block/null.c b/block/null.c
> index ec2bd27..602f93c 100644
> --- a/block/null.c
> +++ b/block/null.c
> @@ -12,8 +12,11 @@
>  
>  #include "block/block_int.h"
>  
> +#define NULL_OPT_LATENCY "latency-ns"
> +
>  typedef struct {
>      int64_t length;
> +    int64_t latency_ns;
>  } BDRVNullState;
>  
>  static QemuOptsList runtime_opts = {
> @@ -30,6 +33,12 @@ static QemuOptsList runtime_opts = {
>              .type = QEMU_OPT_SIZE,
>              .help = "size of the null block",
>          },
> +        {
> +            .name = NULL_OPT_LATENCY,
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "nanoseconds (approximated) to wait "
> +                    "before completing request",
> +        },
>          { /* end of list */ }
>      },
>  };
> @@ -44,6 +53,11 @@ static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
>      qemu_opts_absorb_qdict(opts, options, &error_abort);
>      s->length =
>          qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30);
> +    s->latency_ns =
> +        qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0);
> +    if (s->latency_ns < 0) {
> +        error_setg(errp, "latency-ns is invalid");
> +    }
>      qemu_opts_del(opts);
>      return 0;

If errp is set, we should also return a negative error code.

Kevin