Re: [Qemu-block] [PATCH v3 5/7] block: add throttle block filter driver

[Kevin Wolf]

Am 03.08.2017 um 13:48 hat Manos Pitsidianakis geschrieben:
> On Thu, Aug 03, 2017 at 10:07:41AM +0200, Kevin Wolf wrote:
> > Am 31.07.2017 um 11:54 hat Manos Pitsidianakis geschrieben:
> > > +/* Extract ThrottleConfig options. Assumes cfg is initialized and will be
> > > + * checked for validity.
> > > + */
> > > +static int throttle_extract_options(QemuOpts *opts, ThrottleConfig *cfg,
> > > +                                     Error **errp)
> > > +{
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_BPS_TOTAL)) {
> > > +        cfg->buckets[THROTTLE_BPS_TOTAL].avg =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_BPS_TOTAL,
> > > +                                0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_BPS_READ)) {
> > > +        cfg->buckets[THROTTLE_BPS_READ].avg  =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_BPS_READ,
> > > +                                0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_BPS_WRITE)) {
> > > +        cfg->buckets[THROTTLE_BPS_WRITE].avg =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_BPS_WRITE,
> > > +                                0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_IOPS_TOTAL)) {
> > > +        cfg->buckets[THROTTLE_OPS_TOTAL].avg =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_IOPS_TOTAL,
> > > +                                0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_IOPS_READ)) {
> > > +        cfg->buckets[THROTTLE_OPS_READ].avg =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_IOPS_READ,
> > > +                                0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_IOPS_WRITE)) {
> > > +        cfg->buckets[THROTTLE_OPS_WRITE].avg =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_IOPS_WRITE,
> > > +                                0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_BPS_TOTAL_MAX)) {
> > > +        cfg->buckets[THROTTLE_BPS_TOTAL].max =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_BPS_TOTAL_MAX, 0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_BPS_READ_MAX)) {
> > > +        cfg->buckets[THROTTLE_BPS_READ].max  =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_BPS_READ_MAX, 0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_BPS_WRITE_MAX)) {
> > > +        cfg->buckets[THROTTLE_BPS_WRITE].max =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_BPS_WRITE_MAX, 0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_IOPS_TOTAL_MAX)) 
> > > {
> > > +        cfg->buckets[THROTTLE_OPS_TOTAL].max =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_IOPS_TOTAL_MAX, 0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_IOPS_READ_MAX)) {
> > > +        cfg->buckets[THROTTLE_OPS_READ].max =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_IOPS_READ_MAX, 0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_IOPS_WRITE_MAX)) 
> > > {
> > > +        cfg->buckets[THROTTLE_OPS_WRITE].max =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_IOPS_WRITE_MAX, 0);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_BPS_TOTAL_MAX_LENGTH)) {
> > > +        if (qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_BPS_TOTAL_MAX_LENGTH, 1) > 
> > > UINT_MAX) {
> > > +            error_setg(errp, "%s value must be in the range [0, %u]",
> > > +                       THROTTLE_OPT_PREFIX QEMU_OPT_BPS_TOTAL_MAX_LENGTH,
> > > +                       UINT_MAX);
> > > +            return -1;
> > > +        }
> > > +        cfg->buckets[THROTTLE_BPS_TOTAL].burst_length =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_BPS_TOTAL_MAX_LENGTH, 1);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_BPS_READ_MAX_LENGTH)) {
> > > +        if (qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_BPS_READ_MAX_LENGTH, 1) > 
> > > UINT_MAX) {
> > > +            error_setg(errp, "%s must be in the range [0, %u]",
> > > +                       THROTTLE_OPT_PREFIX QEMU_OPT_BPS_READ_MAX_LENGTH,
> > > +                       UINT_MAX);
> > > +            return -1;
> > > +        }
> > > +        cfg->buckets[THROTTLE_BPS_READ].burst_length  =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_BPS_READ_MAX_LENGTH, 1);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_BPS_WRITE_MAX_LENGTH)) {
> > > +        if (qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_BPS_WRITE_MAX_LENGTH, 1) > 
> > > UINT_MAX) {
> > > +            error_setg(errp, "%s must be in the range [0, %u]",
> > > +                       THROTTLE_OPT_PREFIX QEMU_OPT_BPS_WRITE_MAX_LENGTH,
> > > +                       UINT_MAX);
> > > +            return -1;
> > > +        }
> > > +        cfg->buckets[THROTTLE_BPS_WRITE].burst_length =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_BPS_WRITE_MAX_LENGTH, 1);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_IOPS_TOTAL_MAX_LENGTH)) {
> > > +        if (qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_IOPS_TOTAL_MAX_LENGTH, 1) > 
> > > UINT_MAX) {
> > > +            error_setg(errp, "%s must be in the range [0, %u]",
> > > +                       THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_IOPS_TOTAL_MAX_LENGTH,
> > > +                       UINT_MAX);
> > > +            return -1;
> > > +        }
> > > +        cfg->buckets[THROTTLE_OPS_TOTAL].burst_length =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_IOPS_TOTAL_MAX_LENGTH, 1);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_IOPS_READ_MAX_LENGTH)) {
> > > +        if (qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_IOPS_READ_MAX_LENGTH, 1) > 
> > > UINT_MAX) {
> > > +            error_setg(errp, "%s must be in the range [0, %u]",
> > > +                       THROTTLE_OPT_PREFIX QEMU_OPT_IOPS_READ_MAX_LENGTH,
> > > +                       UINT_MAX);
> > > +            return -1;
> > > +        }
> > > +        cfg->buckets[THROTTLE_OPS_READ].burst_length =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_IOPS_READ_MAX_LENGTH, 1);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_IOPS_WRITE_MAX_LENGTH)) {
> > > +        if (qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_IOPS_WRITE_MAX_LENGTH, 1) > 
> > > UINT_MAX) {
> > > +            error_setg(errp, "%s must be in the range [0, %u]",
> > > +                       THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_IOPS_WRITE_MAX_LENGTH,
> > > +                       UINT_MAX);
> > > +            return -1;
> > > +        }
> > > +        cfg->buckets[THROTTLE_OPS_WRITE].burst_length =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX
> > > +                                QEMU_OPT_IOPS_WRITE_MAX_LENGTH, 1);
> > > +    }
> > > +    if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX QEMU_OPT_IOPS_SIZE)) {
> > > +        cfg->op_size =
> > > +            qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX 
> > > QEMU_OPT_IOPS_SIZE,
> > > +                                0);
> > > +    }
> > > +    return 0;
> > > +}
> > 
> > This function is very repetitive, but each block is long enough that
> > you have to look closely to review whether the right constants are used
> > everywhere.
> > 
> > Maybe this could become a bit more readable with a macro or two?
> 
> How about this?
> 
> 
> #   #define IF_OPT_SET(rvalue,opt_name) \
> #       if (qemu_opt_get(opts, THROTTLE_OPT_PREFIX opt_name)) { \
> #           rvalue = qemu_opt_get_number(opts, THROTTLE_OPT_PREFIX opt_name,
> 0); }
> 
> #       IF_OPT_SET(cfg->buckets[THROTTLE_BPS_TOTAL].avg, QEMU_OPT_BPS_TOTAL);
> #       IF_OPT_SET(cfg->buckets[THROTTLE_BPS_READ].avg, QEMU_OPT_BPS_READ);
> [...]

Looks a lot more readable to me. :-)

If nobody objects, I'd suggest to go this way.

> > > +static int coroutine_fn throttle_co_pwritev(BlockDriverState *bs,
> > > +                                            uint64_t offset, uint64_t 
> > > bytes,
> > > +                                            QEMUIOVector *qiov, int 
> > > flags)
> > > +{
> > > +    ThrottleGroupMember *tgm = bs->opaque;
> > > +    throttle_group_co_io_limits_intercept(tgm, bytes, true);
> > > +
> > > +    return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
> > > +}
> > 
> > I think we want to set BlockDriver.supported_write_flags so that passing
> > down flags is actually of any use.
> 
> Can you explain what you mean? Do you mean doing this in throttle_open():
> 
>    bs->supported_write_flags = bs->file->bs->supported_write_flags;
>    bs->supported_zero_flags = bs->file->bs->supported_zero_flags;

Yes, I think that should do the trick.

Kevin

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