Re: [9fans] A little more ado about async Tclunk

[Bruce Ellis <bruce.ellis@gmail.com>]

right journal. i'll do some unusual tests and report on the results.

wing-commander has to awake early to attend his mother's 80th birthday party.

back to you on this one.

brucee

On Fri, Oct 29, 2010 at 8:45 PM, Gorka Guardiola <paurea@gmail.com> wrote:
> On Fri, Oct 29, 2010 at 11:01 AM, Charles Forsyth <forsyth@terzarima.net> wrote:
>>>What you are saying is that the problem could be something like:
>>
>>>-> Tclunk
>>>(do not wait for response)
>>>-> Topen (the file is exclusive)
>>
>> no, because what actually happens is closer to
>>        A: Topen
>>        ...
>>        queue request to *another process* to send Tclunk
>>        ...
>>        A: Topen
>>
>> leading to either case 1
>>        A: Topen
>>        B: Tclunk
>>        A: Topen
>>
>> or case 2
>>        A: Topen
>>        A: Topen
>>        B: Tclunk
>>
>> depending on the scheduling of the two processes A and B
>>
>> introducing that other process introduces a new race, that simply did not exist before, because
>> that other process didn't exist before. you always got case 1.
>>
>> and indeed, with the test i ran on the modified system usually it gets case 1
>> because of timing, but eventually a case 2 shows up and the second open fails.
>>
>>
>
> That is why I said, (my second message in the thread) that at least
> you should send the Tclunks synchronously.
> Meaning the close system call sends the Tclunk
> and then fires another thread/writes down in a list for another thread
> for the fid to be recollected when the
> answer comes asynchronously.
> This prevents the fid being reused and simultaneously tries
> to keep the operations in the order the client intended.
> Still there are no guarantees, because the
> messages can be reordered in the server but...
> Still, it does not work in general (the server...) and I thought it was not
> profitable enough to be worth the hassle, but then...
>
>> my froggie has been running for four years 24/7. if you haven't read
>> the BLTJ then styx runs over the PCI ... 4  ixp1200s. asynch clunks.
>> the only problem is it's 10 times quicker.
>
> I haven´t read the Journal, I thought it was referring to the Dylan´s song
> putting froggie as an archetype of decency. You are talking about this?:
> http://onlinelibrary.wiley.com/doi/10.1002/bltj.1/pdf
>
> Do you do completely asynch clunks or just the wait for the response?.
> 10 times?, that is some latency. Can you break up exactly where the gain
> comes from?.
>
> G.
>
>