From 61505654942cb9895a9811fde1dcbb662fd7d66a Mon Sep 17 00:00:00 2001 From: Bart Schaefer Date: Sat, 7 May 2011 19:32:57 +0000 Subject: 29175: optimize freeheap --- Src/mem.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) (limited to 'Src') diff --git a/Src/mem.c b/Src/mem.c index 1a3e75997..9b80f188c 100644 --- a/Src/mem.c +++ b/Src/mem.c @@ -220,8 +220,28 @@ freeheap(void) h_free++; #endif + /* At this point we used to do: fheap = NULL; - for (h = heaps; h; h = hn) { + * + * When pushheap() is called, it sweeps over the entire heaps list of + * arenas and marks every one of them with the amount of free space in + * that arena at that moment. zhalloc() is then allowed to grab bits + * out of any of those arenas that have free space. + * + * With the above reset of fheap, the loop below sweeps back over the + * entire heap list again, resetting the free space in every arena to + * the amount stashed by pushheap() and finding the first arena with + * free space to optimize zhalloc()'s next search. When there's a lot + * of stuff already on the heap, this is an enormous amount of work, + * and performance goes to hell. + * + * However, there doesn't seem to be any reason to reset fheap before + * beginning this loop. Either it's already correct, or it has never + * been set and this loop will do it, or it'll be reset from scratch + * on the next popheap(). So all that's needed here is to pick up + * the scan wherever the last pass [or the last popheap()] left off. + */ + for (h = (fheap ? fheap : heaps); h; h = hn) { hn = h->next; if (h->sp) { #ifdef ZSH_MEM_DEBUG @@ -242,7 +262,7 @@ freeheap(void) if (hl) hl->next = NULL; else - heaps = NULL; + heaps = fheap = NULL; unqueue_signals(); } -- cgit 1.4.1