From c61ccd9769c9c83dcdf5f7693af2ca0a605b6e19 Mon Sep 17 00:00:00 2001 From: Kaz Kylheku Date: Sat, 29 Mar 2014 11:44:52 -0700 Subject: Change to how locations are passed around, for the sake of generational GC. The issue being solved here is the accuracy of the gc_set function. The existing impelmentation is too conservative. It has no generation information about the memory location being stored, and so it assumes the worst: that it is a location in the middle of a gen 1 object. This is sub-optimal, creating unacceptable pressure against the checkobj array and, worse, as a consequence causing unreachable gen 0 objects to be tenured into gen 1. To solve this problem, we replace "val *" pointers with a structure of type "loc" which keeps track of the object too, which lets us discover the generation. I tried another approach: using just a pointer with a bitfield indicating the generation. This turned out to have a serious issue: such a bitfield goes stale when the object is moved to a different generation. The object holding the memory location is in gen 1, but the annotated pointer still indicates gen 0. The gc_set function then makes the wrong decision, and premature reclamation takes place. * combi.c (perm_init_common, comb_gen_fun_common, rcomb_gen_fun_common, rcomb_list_gen_fun): Update to new interfaces for managing mutation. * debug.c (debug): Update to new interfaces for managing mutation. Avoid loc variable name. * eval.c (env_fbind, env_fbind): Update to new interfaces for managing mutation. (lookup_var_l, dwim_loc): Return loc type and update to new interfaces. (apply_frob_args, op_modplace, op_dohash, transform_op, mapcarv, mappendv, repeat_infinite_func, repeat_times_func): Update to new interfaces for managing mutation. * eval.h (lookup_var_l): Declaration updated. * filter.c (trie_add, trie_compress, trie_compress_intrinsic, * build_filter, built_filter_from_list, filter_init): Update to new * interfaces. * gc.c (gc_set): Rewritten to use loc type which provides the exact generation. We do not need the in_malloc_range hack any more, since we have the backpointer to the object. (gc_push): Take loc rather than raw pointer. * gc.h (gc_set, gc_push): Declarations updated. * hash.c (struct hash): The acons* functions use loc instead of val * now. (hash_equal_op, copy_hash, gethash_c, inhash, gethash_n, pushhash, Change to how locations are passed around, for the sake of generational GC. The issue being solved here is the accuracy of the gc_set function. The existing impelmentation is too conservative. It has no generation information about the memory location being stored, and so it assumes the worst: that it is a location in the middle of a gen 1 object. This is sub-optimal, creating unacceptable pressure against the checkobj array and, worse, as a consequence causing unreachable gen 0 objects to be tenured into gen 1. To solve this problem, we replace "val *" pointers with a structure of type "loc" which keeps track of the object too, which lets us discover the generation. I tried another approach: using just a pointer with a bitfield indicating the generation. This turned out to have a serious issue: such a bitfield goes stale when the object is moved to a different generation. The object holding the memory location is in gen 1, but the annotated pointer still indicates gen 0. The gc_set function then makes the wrong decision, and premature reclamation takes place. * combi.c (perm_init_common, comb_gen_fun_common, rcomb_gen_fun_common, rcomb_list_gen_fun): Update to new interfaces for managing mutation. * debug.c (debug): Update to new interfaces for managing mutation. Avoid loc variable name. * eval.c (env_fbind, env_fbind): Update to new interfaces for managing mutation. (lookup_var_l, dwim_loc): Return loc type and update to new interfaces. (apply_frob_args, op_modplace, op_dohash, transform_op, mapcarv, mappendv, repeat_infinite_func, repeat_times_func): Update to new interfaces for managing mutation. * eval.h (lookup_var_l): Declaration updated. * filter.c (trie_add, trie_compress, trie_compress_intrinsic, * build_filter, built_filter_from_list, filter_init): Update to new * interfaces. * gc.c (gc_set): Rewritten to use loc type which provides the exact generation. We do not need the in_malloc_range hack any more, since we have the backpointer to the object. (gc_push): Take loc rather than raw pointer. * gc.h (gc_set, gc_push): Declarations updated. * hash.c (struct hash): The acons* functions use loc instead of val * now. (hash_equal_op, copy_hash, gethash_c, inhash, gethash_n, pushhash, --- eval.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'eval.h') diff --git a/eval.h b/eval.h index a46d2a9a..25aa6bc5 100644 --- a/eval.h +++ b/eval.h @@ -33,7 +33,7 @@ val make_env(val fbindings, val vbindings, val up_env); val env_fbind(val env, val sym, val fun); val env_vbind(val env, val sym, val obj); val lookup_var(val env, val sym); -val *lookup_var_l(val env, val sym); +loc lookup_var_l(val env, val sym); val lookup_fun(val env, val sym); val interp_fun(val env, val fun, val args); void reg_var(val sym, val val); -- cgit v1.2.3