Re: [PATCH 1/6] ratelimit: treat zero speed as unlimited

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

10.05.2021 11:59, Emanuele Giuseppe Esposito wrote:
> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> Both users of RateLimit, block-copy.c and blockjob.c, treat
> a speed of zero as unlimited, while RateLimit treats it as
> "as slow as possible".  The latter is nicer from the code
> point of view but pretty useless, so disable rate limiting
> if a speed of zero is provided.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

> ---
>   include/qemu/ratelimit.h | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/include/qemu/ratelimit.h b/include/qemu/ratelimit.h
> index 003ea6d5a3..48bf59e857 100644
> --- a/include/qemu/ratelimit.h
> +++ b/include/qemu/ratelimit.h
> @@ -43,7 +43,11 @@ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
>       double delay_slices;
>   
>       QEMU_LOCK_GUARD(&limit->lock);
> -    assert(limit->slice_quota && limit->slice_ns);
> +    if (!limit->slice_quota) {
> +        /* Throttling disabled.  */
> +        return 0;
> +    }
> +    assert(limit->slice_ns);
>   
>       if (limit->slice_end_time < now) {
>           /* Previous, possibly extended, time slice finished; reset the
> @@ -83,7 +87,11 @@ static inline void ratelimit_set_speed(RateLimit *limit, uint64_t speed,
>   {
>       QEMU_LOCK_GUARD(&limit->lock);
>       limit->slice_ns = slice_ns;
> -    limit->slice_quota = MAX(((double)speed * slice_ns) / 1000000000ULL, 1);
> +    if (speed == 0) {
> +        limit->slice_quota = 0;
> +    } else {
> +        limit->slice_quota = MAX(((double)speed * slice_ns) / 1000000000ULL, 1);
> +    }
>   }
>   
>   #endif
> 


-- 
Best regards,
Vladimir