A doubly-linked list for tracking living threads guarantees
constant-time insert/delete performance with no corner cases of a
hash table. I chose this ccan implementation of doubly-linked
lists over the BSD sys/queue.h implementation since:
1) insertion and removal are both branchless
2) locality is improved if a struct may be a member of multiple lists
(0002 patch in Feature 9632 will introduce a secondary list
for waiting FDs)
This also increases cache locality during iteration: improving
performance in a new IO#close benchmark with many sleeping threads
while still scanning the same number of threads.
vm_thread_close 1.762
* vm_core.h (rb_vm_t): list_head and counter for living_threads
(rb_thread_t): vmlt_node for living_threads linkage
(rb_vm_living_threads_init): new function wrapper
(rb_vm_living_threads_insert): ditto
(rb_vm_living_threads_remove): ditto
* vm.c (rb_vm_living_threads_foreach): new function wrapper
* thread.c (terminate_i, thread_start_func_2, thread_create_core,
thread_fd_close_i, thread_fd_close): update to use new APIs
* vm.c (vm_mark_each_thread_func, rb_vm_mark, ruby_vm_destruct,
vm_memsize, vm_init2, Init_VM): ditto
* vm_trace.c (clear_trace_func_i, rb_clear_trace_func): ditto
* benchmark/bm_vm_thread_close.rb: added to show improvement
* ccan/build_assert/build_assert.h: added as a dependency of list.h
* ccan/check_type/check_type.h: ditto
* ccan/container_of/container_of.h: ditto
* ccan/licenses/BSD-MIT: ditto
* ccan/licenses/CC0: ditto
* ccan/str/str.h: ditto (stripped of unused macros)
* ccan/list/list.h: ditto
* common.mk: add CCAN_LIST_INCLUDES
[ruby-core:61871][Feature 9632 (part 1)]
Apologies for the size of this commit, but I think a good
doubly-linked list will be useful for future features, too.
This may be used to add ordering to a container_of-based hash
table to preserve compatibility if required (e.g. feature 9614).
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45913 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Nobuyoshi Nakada
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