prefetch still broken with readv and paramiko 1.6.1

[Robey Pointer]

On 26 Jul 2006, at 12:13, John Arbash Meinel wrote:

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> Robey Pointer wrote:
>>
>> On 25 Jul 2006, at 9:28, John Arbash Meinel wrote:
>>
>>> Well, I've found a few more bugs in the readv/prefetching logic.
>>
>> Would you try the current bzr trunk?  Located here:
>>
>>     http://www.lag.net/paramiko/bzr/paramiko
>>
>> I took a 90 degree turn, decided to stop explaining how readv is  
>> meant
>> to be used, and  tried to adapt it to how you're using it.  So I'd
>> appreciate feedback on whether that makes it work right for you.
>>
>
> It does work correctly, but unfortunately it makes everything much
> slower. In testing regular seek+read, it slowed down operations  
> from 80s
> to ~100s.

I think my last change (@374) came after your tests, so it might be  
worth pulling paramiko and trying again.  The last change attempts to  
avoid fetching the same data twice if we're queued up to fetch a  
chunk for both prefetch and readv but the data hasn't arrived yet.

I'm about to run to a show but I'll respond to the other half of this  
email later -- I'll need to actually sit down and try stuff out. :)

robey