[tarantool-patches] Re: [PATCH v2 02/11] vinyl: factor load regulator out of quota

[Konstantin Osipov <kostja@tarantool.org>]

* Vladimir Davydov <vdavydov.dev@gmail.com> [18/09/28 21:00]:
> Turned out that throttling isn't going to be as simple as maintaining
> the write rate below the estimated dump bandwidth, because we also need
> to take into account whether compaction keeps up with dumps. Tracking
> compaction progress isn't a trivial task and mixing it in a module
> responsible for resource limiting, which vy_quota is, doesn't seem to be
> a good idea. Let's factor out the related code into a separate module
> and call it vy_regulator. Currently, the new module only keeps track of
> the write rate and the dump bandwidth and sets the memory watermark
> accordingly, but soon we will extend it to configure throttling as well.

OK, if we keep regulator in place there is a few comments about
the contents of the patch (i.e. the renames).

> -	struct vy_quota *q = &env->quota;
> +	struct vy_regulator *r = &env->regulator;
>  
> -	info_table_begin(h, "quota");
> -	info_append_int(h, "used", q->used);
> -	info_append_int(h, "limit", q->limit);
> -	info_append_int(h, "watermark", q->watermark);
> -	info_append_int(h, "use_rate", q->use_rate);
> -	info_append_int(h, "dump_bandwidth", q->dump_bw);
> -	info_table_end(h); /* quota */
> +	info_table_begin(h, "regulator");
> +	info_append_int(h, "watermark", r->watermark);
> +	info_append_int(h, "write_rate", r->write_rate);
> +	info_append_int(h, "dump_bandwidth", r->dump_bw);

I think "watermark" should be now "dump_watermark", sicne simply
"watermark" is not specific enough. Is it regulator watermark? A
regulator watermark doesn't make any sense to me.

The rename should take place across the entire code base imho.

>  	assert(mem_used_after >= mem_used_before);
>  	vy_quota_adjust(&env->quota, tx->write_size,
>  			mem_used_after - mem_used_before);
> +	vy_regulator_check_watermark(&env->regulator);

Like check_dump_watermark.

>  vy_env_quota_exceeded_cb(struct vy_quota *quota)
>  {
>  	struct vy_env *env = container_of(quota, struct vy_env, quota);
> +	vy_regulator_no_memory(&env->regulator);

IMHO vy_regulator_quota_exceeded is a better name.
-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov