[Firebird-devel] Delete by pool and parent_redirect

[Vlad K. <hv...@us...>]

    All,

    Recall thread "Speed difference between 2.1.2 and 2.5.0 again" by Gabor Boros from April 8.
Gabor kindly sent to me script which reproduced problem. I can confirm : SS 2.1.2 executed 
script by 25-27 sec while SS HEAD executed same script by 36-38 sec. The script contains 
mostly INSERTS's and i found that most time engine spend in dsql\prepare.

    Before v2.5 DSQL created own memory pool for every statement. When statement is released
its pool is destroyed too. Sometime at v2.5 stage Dmitry made DSQL pool allocated from common
database pool. It allows to somewhat reduce memory consumption. But this change make DSQL 
pool to redirect most of all small requests to the parent (database) pool. This is tens or even 
hundreds of small memory chunks. When DSQL pool is released it must deallocate all memory 
chunks allocated from parent pool and pass them to the parent pool one-by-one. This is very slow 
of course.

    I disabled "parent_redirect" feature of memory pools and HEAD executed script by 26-28 sec
now. The question is - what should we do in HEAD with it ? I see two options :

a) disable "parent_redirect". It will make HEAD work almost as 2.1, AFAIU

b) rework "parent_redirect" to request medium sized memory chunks from parent pool (say 4-8KB)
    and use it to allocate memory for immediate callers. When such pool is freed it (pool) have to 
    deallocate from parent pool much less number of memory blocks.

Opinions ?

Regards.
Vlad