Re: Backup throttling

Hi,

On 2013-09-03 14:35:18 +0200, Antonin Houska wrote:

> +        /*
> +         * THROTTLING_SAMPLE_MIN / MAX_RATE_LOWER (in seconds) should be the
> +         * longest possible time to sleep.
> +         */
> +        pg_usleep((long) sleep);
> +    else
> +
> +        /*
> +         * The actual transfer rate is below the limit. Negative value would
> +         * distort the adjustment of throttled_last.
> +         */
> +        sleep = 0;
> +
> +    /*
> +     * Only the whole multiples of throttling_sample processed. The rest will
> +     * be done during the next call of this function.
> +     */
> +    throttling_counter %= throttling_sample;
> +    /* Once the (possible) sleep ends, new period starts. */
> +    throttled_last += elapsed + sleep;
> +}

It's probably better to use latches for the waiting, those have properly
defined interruption semantics. Whether pg_usleep will be interrupted is
platform dependant...

Greetings,

Andres Freund