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From "Boxer, Aaron" <Aaron.Bo...@uhn.ca>
Subject RE: ZeroCopyPut mystery
Date Fri, 17 Jan 2014 04:08:57 GMT
> If it is only slower for DVD copies, that seems more like an issue with DVD caching.
>
> Are you sure that the synch and asynch tests both started from exactly the same environment?
>
> What do you mean by environment?  Both tests read the same DVD, after flushing the Windows
OS file cache.

I meant the phsyical environment.

There are other potential hardware caches. For example the DVD drive.

> But, the clients are, of course, set up differently.  Would you like me to post how I
am configuring the clients?
>

What about the DVD cache?
Did you reset the drive?

Did you repeat the tests multiple times?
Sometimes with async first, other times with sync first?


Yes, this is completely repeatable. Each run, I clear the OS file cache, and each time, asynch
is about the same slow rate
compared to synch.


>
>
>
>> Perhaps it has to do with buffer size, thread count, ..... ?
>>
>> -----Original Message-----
>> From: Oleg Kalnichevski [mailto:olegk@apache.org]
>> Sent: Thursday, January 16, 2014 11:15 AM
>> To: HttpClient User Discussion
>> Subject: Re: ZeroCopyPut mystery
>>
>> On Thu, 2014-01-16 at 04:33 +0000, Boxer, Aaron wrote:
>>> Hello,
>>>
>>> When I use ZeroCopyPut with hard drive (spinning disk ) disk files, I get a network
transfer rate of about 250 MBPS for first time read of files; 850 MBPS if the files are already
in the Windows OS file cache. Synchronous put gives me about 30 MBPS.
>>>
>>> But, when I am dealing with files on DVD, I get a network transfer rate of 5
MBPS for first time read of files, and 850 MBPS if files are in the OS file cache.
>>> Synchronous put gives me about 30 MBPS.
>>>
>>> So, in the case of first read of DVD files, synchronous client is superior. 
Synchronous should be faster, because it can read and send at the same time.
>>>
>>> Does this make sense?   It seems a little strange to me.
>>>
>>
>> Aaron,
>>
>> Zero copy data transfer is very platform specific. Java merely provides a common
APIs, which however can have radically different implementations on different platforms and
therefore can have different performance characteristics.
>>
>> I guess these numbers have more to do with Windows than with HttpAsyncClient.
>>
>> Oleg
>>
>>
>>
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