new heap manager mmalloc - Mailing list pgsql-hackers

Hi,

FYI regarding the recent performance issues.

This lib is ported to win32. I don't know, how many unixes are 
supported. Perhaps it's better to reuse something and not to 
reimplementit from scratch. But you are to decide.

forwarded from comp.os.linux.announce

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mmalloc is a heap manager. It is written from a scratch. Main goals were
accurate RAM consuming and performance. Goals achieved using relatively
new virtual memory mapping techniques (known in UNIX wolrd as mmap ;-) and
AVL trees.
 Major advantages of this heap manager:* Trimming and "no commit". mmalloc immediately (not in Windows   world)
releasesall deallocated pages to the system. Also all   allocated pages are not commited, because new areas are just
mapped  in, still not commited and only user program could commit memory. So   the following rule is real true:
"NOUNUSED MEMORY WILL BE CONSUMED".
 
* Best-fit. Best-fit strategy was used. As shown in real world    experiments, best-fit proven to be more accurate than
first-fit.
* AVL Trees. Primary internal structure used for controlling large   blocks (>256 bytes, tunable). So the time consumed
byallocating   new block is proportional to O(log N), where N is the number of memory   fragments. Implementation is in
pureC and optimized.
 
* Small blocks grouped. Small blocks are grouped within pages. This    provides more accurate memory consuming. When
doing100000 times    mmalloc(1) only ~130k of real memory will be allocated.
 
* Smart alignment. Blocks smaller than MALLOC_ALIGN (tunable)   are not aligned. (typical for i386 are blocks <4
bytes).Other   blocks are aligned by MALLOC_ALIGN.
 
* Small overhead. For blocks large blocks overhead is 32 bytes. It is   approximately 12.5% for 256 bytes long block.
Forlarger blocks size   of this control structure is ever less noticed. Small blocks are   grouped within one page and
resultingoverhead is less than   0.2% (8/4096*100).
 
* Pure ANSI-C. Pure ANSI-C without any extensions was used. So library   should be portable. Only vmm functions are not
portable,other library   parts should be.
 

Visit homepage:  http://www.geocities.com/SiliconValley/Circuit/5426/index.html

Valery

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Ciao

Ulrich
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Ulrich Vo"3                                             uvo@uvo.do.eunet.de
                    " As a human being I claim the right                      to be widely inconsistent " John Peel
        
 
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