Commit b7728f32 authored by Wolfgang Bumiller's avatar Wolfgang Bumiller Committed by Stefan Hajnoczi
Browse files

ratelimit: don't align wait time with slices 



It is possible for rate limited writes to keep overshooting a slice's
quota by a tiny amount causing the slice-aligned waiting period to
effectively halve the rate.

Signed-off-by: default avatarWolfgang Bumiller <w.bumiller@proxmox.com>
Reviewed-by: default avatarAlberto Garcia <berto@igalia.com>
Message-id: 20180207071758.6818-1-w.bumiller@proxmox.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 00d09fdb

include/qemu/ratelimit.h

+5 −6
Original line number Diff line number Diff line
@@ -36,7 +36,7 @@ typedef struct { 
static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)

{

    int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);

    uint64_t delay_slices;

    double delay_slices;



    assert(limit->slice_quota && limit->slice_ns);
@@ -55,12 +55,11 @@ static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n) 
        return 0;

    }



    /* Quota exceeded. Calculate the next time slice we may start

     * sending data again. */

    delay_slices = (limit->dispatched + limit->slice_quota - 1) /

        limit->slice_quota;

    /* Quota exceeded. Wait based on the excess amount and then start a new

     * slice. */

    delay_slices = (double)limit->dispatched / limit->slice_quota;

    limit->slice_end_time = limit->slice_start_time +

        delay_slices * limit->slice_ns;

        (uint64_t)(delay_slices * limit->slice_ns);

    return limit->slice_end_time - now;

}