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authorFabian Thorand <fabian@channable.com>2022-01-14 16:54:02 +0100
committerMarge Bot <ben+marge-bot@smart-cactus.org>2022-04-27 10:03:03 -0400
commit5de6be0c9120550aaa15534d0a1466018eff137a (patch)
tree9bb5b07063e6662ca79f48f065b7a593177ec00d /rts
parente39cab6256706e23d1e16177913dae190fe32e4f (diff)
downloadhaskell-5de6be0c9120550aaa15534d0a1466018eff137a.tar.gz
Add note about inefficiency in returnMemoryToOS
Diffstat (limited to 'rts')
-rw-r--r--rts/sm/BlockAlloc.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/rts/sm/BlockAlloc.c b/rts/sm/BlockAlloc.c
index d5651db6d8..d99d01d743 100644
--- a/rts/sm/BlockAlloc.c
+++ b/rts/sm/BlockAlloc.c
@@ -1190,6 +1190,14 @@ uint32_t returnMemoryToOS(uint32_t n /* megablocks */)
uint32_t init_n;
init_n = n;
+ // TODO: This is inefficient because this loop will essentially result in
+ // quadratic runtime behavior: for each call to `freeMBlocks`, the
+ // USE_LARGE_ADDRESS_SPACE implementation of it will walk the internal free
+ // list to insert it at the right position, and thus traverse all previously
+ // inserted values to get to it. We can do better though: both the internal
+ // free list and the `free_mblock_list` here are sorted, so one walk should
+ // be enough.
+
// ToDo: not fair, we free all the memory starting with node 0.
for (node = 0; n > 0 && node < n_numa_nodes; node++) {
bd = free_mblock_list[node];