[Tarantool-patches] [PATCH] memtx: allow quota overuse for truncation

[Ilya Kosarev]

>Вторник, 22 декабря 2020, 16:28 +03:00 от Vladislav Shpilevoy <v.shpilevoy at tarantool.org>:
> 
>> Also I don't understand why can't you do that on the slab arena
>> level. Start allocating only 'huge' slabs if the quota is full, but
>> disabled.
>>
>> Yes, allocation in case of out of quota can be done on more
>> internal level.
>> But the problem is exactly in freeing you mentioned further.
>> We need to free in the right way: If we are allocating with
>> mempool, we need to use mempool_find() properly, while
>> if we are allocating ‘huge’ slab, we need to free it accordingly.
>> So the information about the allocation has to be stored
>> somehow in case we are going to alter it depending on the
>> current state. I don’t see convenient place where we can store
>> it, looks like it will be even worse to store such information
>> in struct tuple itself.
>I don't understand why do you need to store any info. Huge slabs
>existed and were freed before your patch, and all worked fine here.
>How are they found and freed with quota enabled?
Proper huge slabs are actually huge and mempool_find() thus
returns NULL for them and they are freed properly. Here we are
allocating «huge» slabs of the size which is the size of actual
truncate tuples, and it is not really huge. Thus we need specific
info to free it in the right way.
 
 
--
Ilya Kosarev
 
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