code review 103710044: bufio: Writer.ReadFrom uses internal writer's ReadFrom ...

bufio: Writer.ReadFrom uses internal writer's ReadFrom only when buffer is full

Update Issue 6373

[pongad, 2014-07-01 05:59:44]

The benchmark does not look encouraging. The problem is probably that the target
writer is an in-memory buffer. So, putting things in bufio.Writer's buffer
simply means memmove'ing twice instead of once. This optimization might still
makes sense for high-latency writers like HDD or network connection though.

Of course, it's possible that my implementation is just slow. In that case, I
welcome any comment!

benchmark                              old ns/op     new ns/op     delta      
BenchmarkReaderCopyOptimal             187           189           +1.07%     
BenchmarkReaderCopyUnoptimal           313           313           +0.00%     
BenchmarkReaderCopyNoWriteTo           14487         14896         +2.82%     
BenchmarkReaderWriteToOptimal          458           471           +2.84%     
BenchmarkWriterCopyOptimal             195           201           +3.08%     
BenchmarkWriterCopyUnoptimal           269           271           +0.74%     
BenchmarkWriterCopyNoReadFrom          17248         17539         +1.69%     
BenchmarkWriterReadFromNotEmpty        1279          1285          +0.47%     
BenchmarkWriterReadFromSmallChunks     62070         64901         +4.56%     
BenchmarkReaderEmpty                   4151          4204          +1.28%     
BenchmarkWriterEmpty                   4427          4499          +1.63%     
BenchmarkWriterFlush                   20.6          20.9          +1.46%     

benchmark                old allocs     new allocs     delta      
BenchmarkReaderEmpty     3              3              +0.00%     
BenchmarkWriterEmpty     2              2              +0.00%     
BenchmarkWriterFlush     0              0              +0.00%     

benchmark                old bytes     new bytes     delta      
BenchmarkReaderEmpty     4224          4224          +0.00%     
BenchmarkWriterEmpty     4160          4160          +0.00%     
BenchmarkWriterFlush     0             0             +0.00%

[pongad, 2014-07-01 06:01:04]

Hello golang-codereviews@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go

[ruiu, 2014-07-02 00:59:56]

I have a pending patch that does the same thing
as this patch. My patch also uses io.WriterTo
if it's available. Can you review it? I should've
send a ping earlier. Sorry.

https://codereview.appspot.com/79110043

[r, 2014-09-02 18:19:08]

R=close

Superseded by https://codereview.appspot.com/79110043

[gobot, 2014-09-28 05:24:43]

R=golang-dev (assigned by satish.puranam@gmail.com)

[gobot, 2014-12-19 05:08:19]

R=close

To the author of this CL:

The Go project has moved to Gerrit Code Review.

If this CL should be continued, please see the latest version of
https://golang.org/doc/contribute.html for instructions on
how to set up Git and the Go project's Gerrit codereview plugin,
and then create a new change with your current code.

If there has been discussion on this CL, please give a link to it
(golang.org/cl/103710044 is best) in the description in your
new CL.

Thanks very much.