Re: [Tarantool-patches] [PATCH v3] wal: introduce limits on simultaneous writes

[Serge Petrenko via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

10.03.2021 11:18, Konstantin Osipov пишет:
> * Vladislav Shpilevoy via Tarantool-patches <tarantool-patches@dev.tarantool.org> [21/03/09 23:44]:
>> Hi! Thanks for the patch!
>>
>> LGTM.
>>
>>> https://github.com/tarantool/tarantool/issues/5536
>>> https://github.com/tarantool/tarantool/tree/sp/gh-5536-replica-oom
> I don't understand why you need two parameters, size and len. What
> difference does it make how many requests are in the queue? The
> queue is IO and memory bound, not CPU bound, at least not more cpu
> bound than any other subsystem.
>
> Pushing the problem to the user by forcing them to choose not one,
> but two configuration values is poor design. How am I supposed to
> know what is the right value for the option?

After some consideration, let's only leave size.
I've force pushed the changes on the branch.

I've also implemented some kind of a fiber semaphore in a separate 
commit on top.
I'm not sure I like how it turned out, so feel free to throw it away. Or 
keep it.


>
> I guess don't know it either - the patch was not followed by
> a benchmark which would prove the selected defaults are optimal.
>
> Tarantool has an incoming throttling limit which makes the whole
> system work like a clock: it's the fiber  pool size and net msg
> size. They were carefully selected after days and weeks of
> testing.
>
-- 
Serge Petrenko