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Recycle actor heap chunks after GC instead of returning to pool
Before this commit, any unused chunks after actor heap garbage collection would be destroyed and returned to the memory pool immediately for reuse by the runtime or any actor. This commit changes things so that instead of destroying and returning the chunks immediatelly, we assume the actor will likely need more memory as it runs more behaviors and keep the recently unused chunks around in case that happens. This is generally more efficient than destroying a chunk and getting a new one from the memory pool because both destorying a chunk and allocating a new one involve updating the pagemap for the chunk to indicate which actor owns the chunk. Updating the pagemap is an expensive operation which we can avoid if we recycle the chunks instead. The main drawback is that since actors will no longer return chunks to the memory pool immediately after a GC, the overall system might end up using more memory as any freed chunks can only be reused by the actor that owns them and the runtime and other actors can no longer reuse that memory as they previously might have been able to.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,124 @@ | ||
| #ifndef mem_heap_chunk_sorting_h | ||
| #define mem_heap_chunk_sorting_h | ||
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| #include "heap.h" | ||
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| /* | ||
| * Shamelessly stolen/adapted from Simon Tatham from: | ||
| * https://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.c | ||
| * | ||
| * This file is copyright 2001 Simon Tatham. | ||
| * | ||
| * Permission is hereby granted, free of charge, to any person | ||
| * obtaining a copy of this software and associated documentation | ||
| * files (the "Software"), to deal in the Software without | ||
| * restriction, including without limitation the rights to use, | ||
| * copy, modify, merge, publish, distribute, sublicense, and/or | ||
| * sell copies of the Software, and to permit persons to whom the | ||
| * Software is furnished to do so, subject to the following | ||
| * conditions: | ||
| * | ||
| * The above copyright notice and this permission notice shall be | ||
| * included in all copies or substantial portions of the Software. | ||
| * | ||
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, | ||
| * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES | ||
| * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND | ||
| * NONINFRINGEMENT. IN NO EVENT SHALL SIMON TATHAM BE LIABLE FOR | ||
| * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF | ||
| * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | ||
| * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | ||
| * SOFTWARE. | ||
| */ | ||
| static large_chunk_t* sort_large_chunk_list_by_size(large_chunk_t *list) | ||
| { | ||
| large_chunk_t *p, *q, *e, *tail; | ||
| int32_t insize, nmerges, psize, qsize, i; | ||
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| /* | ||
| * Silly special case: if `list' was passed in as NULL, return | ||
| * NULL immediately. | ||
| */ | ||
| if (!list) | ||
| return NULL; | ||
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| insize = 1; | ||
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| while (true) | ||
| { | ||
| p = list; | ||
| list = NULL; | ||
| tail = NULL; | ||
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| nmerges = 0; /* count number of merges we do in this pass */ | ||
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| while (NULL != p) | ||
| { | ||
| nmerges++; /* there exists a merge to be done */ | ||
| /* step `insize' places along from p */ | ||
| q = p; | ||
| psize = 0; | ||
| for (i = 0; i < insize; i++) | ||
| { | ||
| psize++; | ||
| q = q->next; | ||
| if (NULL == q) | ||
| break; | ||
| } | ||
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| /* if q hasn't fallen off end, we have two lists to merge */ | ||
| qsize = insize; | ||
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| /* now we have two lists; merge them */ | ||
| while (psize > 0 || (qsize > 0 && (NULL != q))) | ||
| { | ||
| /* decide whether next element of merge comes from p or q */ | ||
| if (psize == 0) | ||
| { | ||
| /* p is empty; e must come from q. */ | ||
| e = q; | ||
| q = q->next; | ||
| qsize--; | ||
| } else if (qsize == 0 || !q) { | ||
| /* q is empty; e must come from p. */ | ||
| e = p; | ||
| p = p->next; | ||
| psize--; | ||
| } else if (p->size <= q->size) { | ||
| /* First element of p is lower (or same); | ||
| * e must come from p. */ | ||
| e = p; | ||
| p = p->next; | ||
| psize--; | ||
| } else { | ||
| /* First element of q is lower; e must come from q. */ | ||
| e = q; | ||
| q = q->next; | ||
| qsize--; | ||
| } | ||
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| /* add the next element to the merged list */ | ||
| if (NULL != tail) | ||
| tail->next = e; | ||
| else | ||
| list = e; | ||
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| tail = e; | ||
| } | ||
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| /* now p has stepped `insize' places along, and q has too */ | ||
| p = q; | ||
| } | ||
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| tail->next = NULL; | ||
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| /* If we have done only one merge, we're finished. */ | ||
| if (nmerges <= 1) /* allow for nmerges==0, the empty list case */ | ||
| return list; | ||
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| /* Otherwise repeat, merging lists twice the size */ | ||
| insize *= 2; | ||
| } | ||
| } | ||
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| #endif |