From: normalperson@... Date: 2016-12-29T01:11:09+00:00 Subject: [ruby-core:78898] [Ruby trunk Bug#13085] io.c io_fwrite creates garbage Issue #13085 has been reported by Eric Wong. ---------------------------------------- Bug #13085: io.c io_fwrite creates garbage https://bugs.ruby-lang.org/issues/13085 * Author: Eric Wong * Status: Open * Priority: Normal * Assignee: * Target version: * ruby -v: * Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN ---------------------------------------- Relying on rb_str_new_frozen for unconverted strings does not save memory because copy-on-write is always triggered in read-write I/O loops were subsequent IO#read calls will clobber the given write buffer. buf = ''.b while input.read(16384, buf) output.write(buf) end This generates a lot of garbage starting with Ruby 2.2 (r44471). For my use case, even IO.copy_stream generates garbage, since I wrap "write" to do Digest calculation in a single pass. I tried using rb_str_replace and reusing the string as a hidden (klass == 0) thread-local, but rb_str_replace attempts CoW optimization by creating new frozen objects, too: https://80x24.org/spew/20161229004417.12304-1-e@80x24.org/raw So, I'm not sure what to do, temporal locking seems wrong for writing strings (I guess it's for reading?). I get test_threaded_flush failures with the following: https://80x24.org/spew/20161229005701.9712-1-e@80x24.org/raw IO#syswrite has the same problem with garbage. I can use IO#write_nonblock on fast filesystems while holding GVL, I guess... -- https://bugs.ruby-lang.org/ Unsubscribe: