From: ko1@... Date: 2018-05-01T02:31:15+00:00 Subject: [ruby-core:86787] [Ruby trunk Feature#14723] [WIP] sleepy GC Issue #14723 has been updated by ko1 (Koichi Sasada). My concerns are: (1) Full GC (like GC.start) or step incremental marking/sweeping (to guarantee (or to reduce) the worst stopping time because of GC for every IO operation). (2) How to know GC is required (if we invoke GC.start on any I/O (blocking) operations, it should be harmful) Seeing your comment #2, > Therefore, if GVL is uncontended and GC has work to-do, we use > zero-timeout ppoll and do incremental GC work (incremental mark > + lazy sweep) as long as we need to wait on FD. they should be: (1) do a step for incremental marking/sweeping (2) only when incremental marking or sweeping They are very reasonable for me. My understanding, your proposal in pseudo code is (pls correct me if it is wrong): ``` def io_operation while true if !GVL.contended? && GC.has_incremental_task? if result = io_operation(timeout: 0) > 0 # timeout = 0 means return immediately # There are result return result else GC.do_step end else GVL.release io_operation(timeout = long time) GVL.acquire end end end ``` No problem for me. However, your code https://80x24.org/spew/20180429035007.6499-3-e@80x24.org/raw ``` +int +rb_gc_step(const rb_execution_context_t *ec) +{ + rb_objspace_t *objspace = rb_ec_vm_ptr(ec)->objspace; + + gc_rest(objspace); + + return rb_gc_inprogress(ec); +} ``` `gc_rest()` do all of rest steps. Is it intentional? Another tiny comments: > + static const struct timespec zero; `zero` doesn't seem to be initialized. intentional? ---- Note: After introducing Guild, getting `contended` status should be high-cost (we need to use lock to see this info). However, we can eliminate this check if we shrink the target: only have one Guild (== current MRI). ---------------------------------------- Feature #14723: [WIP] sleepy GC https://bugs.ruby-lang.org/issues/14723#change-71746 * Author: normalperson (Eric Wong) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- The idea is to use "idle time" when process is otherwise sleeping and using no CPU time to perform GC. It makes sense because real world traffic sees idle time due to network latency and waiting for user input. Right now, it's Linux-only. Future patches will affect other sleeping functions: IO.select, Kernel#sleep, Thread#join, Process.waitpid, etc... I don't know if this patch can be implemented for win32, right now it's just dummy functions and that will be somebody elses job. But all pthreads platforms should eventually benefit. Before this patch, the entropy-dependent script below takes 95MB consistently on my system. Now, depending on the amount of entropy on my system, it takes anywhere from 43MB to 75MB. I'm using /dev/urandom to simulate real-world network latency variations. There is no improvement when using /dev/zero because the process is never idle. require 'net/http' require 'digest/md5' Thread.abort_on_exception = true s = TCPServer.new('127.0.0.1', 0) len = 1024 * 1024 * 1024 th = Thread.new do c = s.accept c.readpartial(16384) c.write("HTTP/1.0 200 OK\r\nContent-Length: #{len}\r\n\r\n") IO.copy_stream('/dev/urandom', c, len) c.close end addr = s.addr Net::HTTP.start(addr[3], addr[1]) do |http| http.request_get('/') do |res| dig = Digest::MD5.new res.read_body { |buf| dig.update(buf) } puts dig.hexdigest end end The above script is also dependent on net/protocol using read_nonblock. Ordinary IO objects will need IO#nonblock=true to see benefits (because they never hit rb_wait_for_single_fd) * gc.c (rb_gc_inprogress): new function (rb_gc_step): ditto * internal.h: declare prototypes for new gc.c functions * thread_pthread.c (gvl_contended_p): new function * thread_win32.c (gvl_contended_p): ditto (dummy) * thread.c (rb_wait_for_single_fd w/ ppoll): use new functions to perform GC while GVL is uncontended and GC is lazy sweeping or incremental marking [ruby-core:86265] ``` 2 part patch broken out https://80x24.org/spew/20180429035007.6499-2-e@80x24.org/raw https://80x24.org/spew/20180429035007.6499-3-e@80x24.org/raw Also on my "sleepy-gc" git branch @ git://80x24.org/ruby.git ---Files-------------------------------- sleepy-gc-wip-v1.diff (5.37 KB) -- https://bugs.ruby-lang.org/ Unsubscribe: