Justtechjobs.com Find a programming school near you






Online Campus Both


php-developer-list | 2002112

Re: [PHP-DEV] Zend fast cache From: George Schlossnagle (george <email protected>)
Date: 11/30/02

> The problem I see with an array approach from an api perspective is
> simply when a bucket
> is free'd, in order to have efficient memory usage, we'd need a second
> level array scan
> for every ALLOC_ZVAL().
>
> Perhaps a linked list would be a better choice for this, as we can
> just be smart about bucket
> access, and eliminate the need for a scan (could be possible I'm
> missing something?)

A number of memory allocators use a multi-tiered page table for this.
basically for each object type you have a array of N pointers to level
1 objects and a freelist for them, basically tier one has N elements
that each contain a freelist bitmask value and an array of pointers to
level 2 objects. Level 2 objects have a freelist of N allocations for
the desired object type and pointers to each of them. This may be what
Andi was talking about, but it wasn't clear to me from his description.

So you get N^3 aloocations you can track, and a freelist search
involves looking at 3 bitmasks. Significantly faster than a linked
list implementation. By keeping a separate tree for each allocation
type (or at least allocation size), you also end up with basically no
fragmentation.

>
> -Sterling
>
> --
> PHP Development Mailing List <http://www.php.net/>
> To unsubscribe, visit: http://www.php.net/unsub.php
> 

-- 
PHP Development Mailing List <http://www.php.net/>
To unsubscribe, visit: http://www.php.net/unsub.php