ref: 75162b207cf3012bfa26d064787026bb044ad220
parent: 2da5de43f610bfd33116a06631a4eaa85deb811d
author: Ori Bernstein <[email protected]>
date: Mon Nov 20 15:33:32 EST 2017
Fix bigalloc bugs. It was sometimes not unmapping things right, and sometimes being overly pessimistic about caching.
--- a/lib/std/bytealloc.myr
+++ b/lib/std/bytealloc.myr
@@ -171,7 +171,11 @@
var p
p = Failmem
- sz = align(sz, Align)
+ /*
+ We need to round up to the page size so that unmapping
+ doesn't end up taking out the tail of another allocation.
+ */
+ sz = align(sz, Pagesz)
/* check our cache */
lock(memlck)
@@ -180,9 +184,15 @@
continue
;;
p = cache[i].p
- if cache[i].sz - sz >= Bktmax
+ /*
+ There's no point splitting a chunk if it's smaller than
+ bktmax, since the allocator will never try using it.
+ */
+ if sz - cache[i].sz > Bktmax
cache[i].sz -= sz
cache[i].p = ((p : intptr) + (sz : intptr) : byte#)
+ else
+ cache[i].sz = 0
;;
break
;;
@@ -200,45 +210,50 @@
}
const bigfree = {p, sz- var minsz, minp, minidx
+ var evictsz, evictp, evictidx
var endp, endblk
- minp = p
- minidx = -1
- minsz = align(sz, Align)
+ sz = align(sz, Pagesz)
+ evictp = p
+ evictidx = -1
+ evictsz = sz
endp = ((p : intptr) + (sz : intptr) : byte#)
lock(memlck)
for var i = 0; i < cache.len; i++
endblk = ((cache[i].p : intptr) + (sz : intptr) : byte#)
- /* try to merge with a saved block */
+ /* merge in front of existing block */
if cache[i].p == endp
cache[i].sz += sz
cache[i].p = p
- minsz = 0
+ evictidx = -1
break
+ /* merge in behind existing block */
elif endblk == p
cache[i].sz += sz
- minsz = 0
+ evictidx = -1
break
;;
- /* check for merges */
- if cache[i].sz < minsz
- minsz = cache[i].sz
- minp = cache[i].p
- minidx = i
+ /* evict */
+ if cache[i].sz < evictsz
+ evictidx = i
+ evictsz = cache[i].sz
+ evictp = cache[i].p
;;
;;
- unlock(memlck)
- /* size of 0 means we found a slot. */
- if minsz == 0
- -> void
+ if evictidx != -1
+ cache[evictidx].p = p
+ cache[evictidx].sz = sz
;;
+ unlock(memlck)
- freemem(minp, minsz)
- if minidx >= 0
- cache[minidx].p = p
- cache[minidx].sz = sz
+ /*
+ Now that we've removed it, we can
+ free it. It's not in the cache, so
+ we don't need the lock held.
+ */
+ if evictsz > 0
+ freemem(evictp, evictsz)
;;
}