High CPU usage on dial-up connections

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High CPU usage on dial-up connections

Majzik Matyas
Hi,

I have a problem using OpenSSL on Windows platform. Version 0.9.7g and
0.9.8.

I created a simple file transfer application which transfers files
between  two computers using SSL connection. This is a multithreaded
application and the file transfer separated to an other thread in this
application. It works perfectly using broadband connection utilizing
minimal CPU usage but when I use dial-up connections (I mean 56k modem)
then the CPU usage on the modem side is always 100% and on the server
side the CPU usage is sometimes 50% sometimes 100% always varying
during the file transfer.

I cannot explain why. Do you have any experience with this problem?

--
Matyas Majzik
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RE: High CPU usage on dial-up connections

Ted Mittelstaedt

Get a real modem.  Your probably using a winmodem which does all
the host processing in the computer CPU.  Also, encrypted data isn't very
compressible so you should turn off both ppp and "hardware" compression.

Many winmodems upchuck when you try to run them with hardware compression
disabled.

Ted

>-----Original Message-----
>From: [hidden email]
>[mailto:[hidden email]]On Behalf Of Matyas Majzik
>Sent: Sunday, July 31, 2005 1:01 AM
>To: [hidden email]
>Subject: High CPU usage on dial-up connections
>
>
>Hi,
>
>I have a problem using OpenSSL on Windows platform. Version 0.9.7g and
>0.9.8.
>
>I created a simple file transfer application which transfers files
>between  two computers using SSL connection. This is a multithreaded
>application and the file transfer separated to an other thread in this
>application. It works perfectly using broadband connection utilizing
>minimal CPU usage but when I use dial-up connections (I mean 56k modem)
>then the CPU usage on the modem side is always 100% and on the server
>side the CPU usage is sometimes 50% sometimes 100% always varying
>during the file transfer.
>
>I cannot explain why. Do you have any experience with this problem?
>
>--
>Matyas Majzik
>______________________________________________________________________
>OpenSSL Project                                 http://www.openssl.org
>User Support Mailing List                    [hidden email]
>Automated List Manager                           [hidden email]
>

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RE: High CPU usage on dial-up connections

JoelKatz
In reply to this post by Majzik Matyas

> Hi,
>
> I have a problem using OpenSSL on Windows platform. Version 0.9.7g and
> 0.9.8.
>
> I created a simple file transfer application which transfers files
> between  two computers using SSL connection. This is a multithreaded
> application and the file transfer separated to an other thread in this
> application. It works perfectly using broadband connection utilizing
> minimal CPU usage but when I use dial-up connections (I mean 56k modem)
> then the CPU usage on the modem side is always 100% and on the server
> side the CPU usage is sometimes 50% sometimes 100% always varying
> during the file transfer.
>
> I cannot explain why. Do you have any experience with this problem?

        Most likely you are using non-blocking sockets and spinning, waiting for
data to be received or sent. Broadband connections empty the buffers faster,
so you spend time waiting for handoffs rather than buffers. Profile and see
what the CPU is doing.

        DS


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RE: High CPU usage on dial-up connections

Chris Fowler-2
On Sun, 2005-07-31 at 15:23 -0700, David Schwartz wrote:

> Most likely you are using non-blocking sockets and spinning, waiting for
> data to be received or sent. Broadband connections empty the buffers faster,
> so you spend time waiting for handoffs rather than buffers. Profile and see
> what the CPU is doing.
>

This sounds about right.  If you are using Java and NIO this might be
the case.  Java NIO does use non-blocking I/O.

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