Re: cvs commit: src/sys/conf files src/sys/sys alist.h src/sys/kern subr_alist.c

[Jason Smethers <jason@xxxxxxxxxxxx>]

Matthew Dillon wrote:
> dillon      2007/04/09 10:10:00 PDT
>
> DragonFly src repository
>
>   Modified files:
>     sys/conf             files 
>   Added files:
>     sys/sys              alist.h 
>     sys/kern             subr_alist.c 
>   Log:

Allocations of size greater than the radix seem to be returning the 
wrong starting block. Should the allocator return the starting block at 
which it allocated from? If so, sys/kern/subr_alist.c at line 393 should 
be changed to the following (or similar):

		mask = (u_daddr_t)-1 >> (ALIST_BMAP_RADIX - n);
		for (j = 0; j < ALIST_META_RADIX; j += n / 2) {
			if ((scan->bm_bitmap & mask) == mask) {
				scan->bm_bitmap &= ~mask;
				return blk; // <== here
			}
			mask <<= n;
			blk += radix * n / 2; // <== here
		}


Also, there appears to be a redundent check for a terminating block at 
line 442: the first check is at the start of the for loop on line 412. 
Removing it shows a 4-5% speed up on allocation from an average of 220ms 
 down to an average of 210ms per allocation for sequential single block 
allocations on an Athlon X2 2Ghz.


- Jason