Notable performance improvement in 64-bit build

Notable performance improvement in 64-bit build

[Ivan Todoroski]

Hello everyone,

I'm just curious, has there been any special focus on performance
improvements in the 64-bit version compared to 32-bit?

I'm asking because I recently upgraded from 32-bit to 64-bit Cygwin, and I
noticed that my bash prompt would show up noticeably quicker when I opened a
new Cygwin shell (I have a rather complicated ~/.profile script, so the
delay is actually visible to the eye).

At first I thought it was just some sort of placebo effect and I was
imagining it, but the effect seemed so persistent that I just had to perform
some measurements.

What I found was that under 32-bit Cygwin my ~/.profile script is executed
in 507ms (average of 30 runs), but under 64-bit Cygwin the exact same script
gets executed in 376ms (again, 30-run average). Both measurements were done
on the same machine with 32-bit and 64-bit Cygwin installed side by side
(both freshly updated to their latest respective versions).

That's a whopping 33% performance improvement!

So I was just curious if anyone had any speculations on what exactly might
have caused this performance increase. :)

In any case, kudos to the Cygwin developers, great job on the 64-bit build!


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Re: Notable performance improvement in 64-bit build

[Corinna Vinschen]

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On Nov 12 00:52, Ivan Todoroski wrote:
> Hello everyone,
> 
> I'm just curious, has there been any special focus on performance
> improvements in the 64-bit version compared to 32-bit?
> 
> I'm asking because I recently upgraded from 32-bit to 64-bit Cygwin, and I
> noticed that my bash prompt would show up noticeably quicker when I opened a
> new Cygwin shell (I have a rather complicated ~/.profile script, so the
> delay is actually visible to the eye).
> 
> At first I thought it was just some sort of placebo effect and I was
> imagining it, but the effect seemed so persistent that I just had to perform
> some measurements.
> 
> What I found was that under 32-bit Cygwin my ~/.profile script is executed
> in 507ms (average of 30 runs), but under 64-bit Cygwin the exact same script
> gets executed in 376ms (again, 30-run average). Both measurements were done
> on the same machine with 32-bit and 64-bit Cygwin installed side by side
> (both freshly updated to their latest respective versions).
> 
> That's a whopping 33% performance improvement!
> 
> So I was just curious if anyone had any speculations on what exactly might
> have caused this performance increase. :)

Uhm... actually we don't know exactly either.  It is said that the WOW64
emulation may introduce a 5% penalty, but that doesn't explain 33%.  I
made some tests on my own and I had performance differences of a meager
1% and up to 83% in various different `make' scenarios, so I guess it's
not quite a safe bet to say 64 bit Cygwin is faster.  But all in all
we're rather happy with the result.

You may be interested to update to the test release 1.7.33, see
https://cygwin.com/ml/cygwin-announce/2014-11/msg00013.html

It introduces two changes, one in terms of user and group account
handling which should speed up process startup noticably, the other a
change in exception handling which should speed up the 64 bit version by
removing some code overhead per system call.

> In any case, kudos to the Cygwin developers, great job on the 64-bit build!

Thanks a lot!


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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Re: Notable performance improvement in 64-bit build

[Csaba Raduly]

Hi Ivan,

On Wed, Nov 12, 2014 at 12:52 AM, Ivan Todoroski wrote:
> Hello everyone,
>
> I'm just curious, has there been any special focus on performance
> improvements in the 64-bit version compared to 32-bit?
>
> I'm asking because I recently upgraded from 32-bit to 64-bit Cygwin, and I
> noticed that my bash prompt would show up noticeably quicker when I opened a
> new Cygwin shell (I have a rather complicated ~/.profile script, so the
> delay is actually visible to the eye).

Do you have the same .profile in both installations?
Do you have the same bash-completion package (often the most
time-consuming part of bash startup)?

Csaba
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Re: Notable performance improvement in 64-bit build

[Ivan Todoroski]

Csaba Raduly writes:

> Do you have the same .profile in both installations?

Yes, the two installations are actually sharing the same home dir, I have
both of them configured to use HOME=%USERPROFILE%.

> Do you have the same bash-completion package (often the most
> time-consuming part of bash startup)?

I don't have the "bash-completion" package installed at all, neither in
the 32-bit nor 64-bit installs. I just double checked this now.

Also, I didn't mention this in the original mail, but to make sure I was
comparing apples to apples I actually put "set -x" at the top of the
.profile script, then I ran it under the 32-bit and 64-bit installs and
compared the outputs using "diff", to make sure the exact sequence of
steps was executed in both cases. Of course I removed the "set -x" for
the actual benchmark measurements.



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