Issue #5995 has been updated by Yusuke Endoh.


Hello, Martin

I guess that your point is off topic from this ticket.
As I and Masaki showed, in normal cases, File#read does
not reallocate a memory.  (Let me know if I'm wrong)

But I think your point is valid for the general IO#read
(especially, reading from a socket).  I recommend you to
create a patch and a benchmark, and discuss in another
thread.

-- 
Yusuke Endoh <mame / tsg.ne.jp>
----------------------------------------
Feature #5995: calling io_advise_internal() in read_all()
https://bugs.ruby-lang.org/issues/5995

Author: Masaki Matsushita
Status: Rejected
Priority: Normal
Assignee: Motohiro KOSAKI
Category: core
Target version: 


=begin
I propose to call io_advise_internal() in read_all().
It will increase performance.

I created a dummy file:
 dd if=/dev/zero of=dummy bs=1M count=100

Then, I ran the following:

 require 'benchmark'
 
 Benchmark.bm do |x|
   x.report do
     f = File.open("dummy") # dummy file(about 100MB )
     f.read
   end
 end

I freed page cache before each test:
 sudo sysctl -w vm.drop_caches=1

results on Ubuntu 11.10(3.0.0-15-server):

r34462:

 user     system      total        real
   0.050000   0.220000   0.270000 (  0.356033)
 
       user     system      total        real
   0.050000   0.190000   0.240000 (  0.332243)

       user     system      total        real
   0.060000   0.210000   0.270000 (  0.347758)

patched ruby:

 user     system      total        real
   0.030000   0.130000   0.160000 (  0.225866)

       user     system      total        real
   0.040000   0.170000   0.210000 (  0.250172)

       user     system      total        real
   0.040000   0.150000   0.190000 (  0.254654)

It shows the patch increases performance.
=end


-- 
http://bugs.ruby-lang.org/