From: samuel@... Date: 2019-07-12T02:15:04+00:00 Subject: [ruby-core:93703] [Ruby master Feature#15997] Improve performance of fiber creation by using pool allocation strategy. Issue #15997 has been updated by ioquatix (Samuel Williams). To run benchmarks: ``` make benchmark ITEM=vm2_fiber ``` ---------------------------------------- Feature #15997: Improve performance of fiber creation by using pool allocation strategy. https://bugs.ruby-lang.org/issues/15997#change-79323 * Author: ioquatix (Samuel Williams) * Status: Open * Priority: Normal * Assignee: ko1 (Koichi Sasada) * Target version: ---------------------------------------- https://github.com/ruby/ruby/pull/2224 This PR improves the performance of fiber allocation and reuse by implementing a better stack cache. As per @ko1's request, we also increased fiber stack size to be the same as thread stack size. The fiber pool manages a singly linked list of fiber pool allocations. The fiber pool allocation contains 1 or more stack (typically more, e.g. 512). It uses N^2 allocation strategy. ``` // // base = +-------------------------------+-----------------------+ + // |VM Stack |VM Stack | | | // | | | | | // | | | | | // +-------------------------------+ | | // |Machine Stack |Machine Stack | | | // | | | | | // | | | | | // | | | . . . . | | size // | | | | | // | | | | | // | | | | | // | | | | | // | | | | | // +-------------------------------+ | | // |Guard Page |Guard Page | | | // +-------------------------------+-----------------------+ v // // +-------------------------------------------------------> // // count // ``` The performance improvement depends on usage: ``` Calculating ------------------------------------- compare-ruby built-ruby vm2_fiber_allocate 132.900k 180.852k i/s - 100.000k times in 0.752447s 0.552939s vm2_fiber_count 5.317k 110.724k i/s - 100.000k times in 18.806479s 0.903145s vm2_fiber_reuse 160.128 347.663 i/s - 200.000 times in 1.249003s 0.575269s vm2_fiber_switch 13.429M 13.490M i/s - 20.000M times in 1.489303s 1.482549s Comparison: vm2_fiber_allocate built-ruby: 180851.6 i/s compare-ruby: 132899.7 i/s - 1.36x slower vm2_fiber_count built-ruby: 110724.3 i/s compare-ruby: 5317.3 i/s - 20.82x slower vm2_fiber_reuse built-ruby: 347.7 i/s compare-ruby: 160.1 i/s - 2.17x slower vm2_fiber_switch built-ruby: 13490282.4 i/s compare-ruby: 13429100.0 i/s - 1.00x slower ``` The test in summary is run on Linux server with 64GB memory and 4-core Xeon (Intel Xeon CPU E3-1240 v6 @ 3.70GHz). "compare-ruby" is `master`, and "built-ruby" is `master+fiber-pool`. Additionally, we conservatively use `madvise(free)` to avoid swap space usage for unused fiber stacks. However, if you remove this requirement, we can get 6x - 10x performance improvement in `vm2_fiber_reuse` benchmark. There are some options to deal with this (e.g. moving it to `GC.compact`) but as this is still a net win, I'd like to merge this PR as is. -- https://bugs.ruby-lang.org/ Unsubscribe: