Messages in this thread | | | Subject | Re: [PATCH 1/2] lib: more scalable list_sort() | From | Artem Bityutskiy <> | Date | Thu, 21 Jan 2010 11:22:55 +0200 |
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On Wed, 2010-01-20 at 20:51 -0800, Don Mullis wrote: > The use of list_sort() by UBIFS looks like it could generate long > lists; this alternative implementation scales better, reaching ~3x > performance gain as list length approaches the L2 cache size. > > Stand-alone program timings were run on a Core 2 duo L1=32KB L2=4MB, > gcc-4.4, with flags extracted from an Ubuntu kernel build. Object > size is 552 bytes versus 405 for Mark J. Roberts' code. > > Worst case for either implementation is a list length just over a POT, > and to roughly the same degree, so here are results for a range of > 2^N+1 lengths. List elements were 16 bytes each including malloc > overhead; random initial order. >
Could you please add a debugging function which would be compiled-out normally, and which would check that on the output 'list_sort()' gives really sorted list, and number of elements in the list stays the same. You'd call this function before returning from list_sort(). Something like:
#ifdef DEBUG_LIST_SORT static int list_check(void *priv, struct list_head *head, int (*cmp)(void *priv, struct list_head *a, struct list_head *b)) { /* Checking */ } #else #define list_check(priv, head, cmp) 0 #endif
This will provide more confidence in the algorithm correctness for everyone who modifies 'list_sort()'.
-- Best Regards, Artem Bityutskiy (Артём Битюцкий)
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