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Re: wait_for_file ?? [who/what/where does fclose()?]
From: |
Shai Ayal |
Subject: |
Re: wait_for_file ?? [who/what/where does fclose()?] |
Date: |
Fri, 10 Sep 2010 23:08:45 +0300 |
On Fri, Sep 10, 2010 at 10:49 PM, Michael D Godfrey
<address@hidden> wrote:
> On 09/10/2010 12:26 PM, John W. Eaton wrote:
>
> So, back to the question I asked yesterday:
>
> What were the specifics of the case(s) that were failing? What types
> of systems, filesystems, etc.? If it only occurred on network mounted
> filesystems that have the async option set, then I guess I'm not
> surprised by the failure.
>
> If the problem also happened on local filesystems, or NFS filesystems
> with the sync option set, then I'm not sure why it would happen, or
> how to avoid the problem.
>
> I think we need to understand why the original failure that prompted
> this discussion occurred.
>
> An additional thought is that if these failures only happened on
> network mounted filesystems that have the async option set, then I'm
> not sure we should work too hard at tring to fix all the potential
> problems that can occur with that option. It's probably better to
> recommend that people avoid using the option, or if they do and odd
> failures happen, then it is not Octave's fault.
>
> jwe
>
> John,
>
> I am at least partly to blame for this. I noticed problems using ssh, with
> or without NFS being involved. But, the case that I tried to focus on was
> when running Octave in an NX window on a server which had all local
> storage (no NFS involved). This is a simpler case than anything with
> NFS (note that it is not just async, but also whether "hard" mount option is
> used and whether NFS locking is working, and...)
>
> So, the NX case has shown this problem because the drawing time
> to the screen, particularly for graphics, can be very long when compared to
> a
> local real screen or even X11 remotely. And, or course, I focused on NX
> as we use it all the time these days. In the NX case, the original failure
> was due to the fact that the sequence:
>
> drawnow("eps", fid)
> system("gs ....... option referencing .eps file generated by drawnow'")
>
> had the effect that the drawnow did not even do the fopen("*.eps") by the
> time the gs command was run. Trying to put in a test of whether the
> drawnow
> had written the eps file was very unreliable since drawnow, in fact, tended
> to
> wait until Octave returned to the command prompt before creating the eps
> file.
> Shai reports that there is no way to convince fltk to do the file write
> synchronously.
> It does it "when it decides to."
>
> The pipe mechanism appears to be working and, as you pointed out, is
> a cleaner and more efficient way of doing this.
>
> Oh, I should mention the NX normally uses ssh as its client-server protocol,
> but
> this is really not relevant except that it is part of the timing issue. NX
> is VERY
> reliable, even on low bandwidth DSL.
>
I think the point here is not that the file system has long latencies
and is asynchronous, but by using NX, the X server becomes async and
with long latencies. Since drawnow depends on fltk redraws and this in
turn depends on X server request redrawing and such. A highly
optimized X server such as NX might do all sort of interesting
manipulation on the messaging between the X server and client.
So my guess would be that a lot of this confusing timings are because
of NX. perhapse Michael could check the same with just simple X11
forwarding of ssh (ssh -X) which will still give us high latency, but
no optimizations.
Shai
- Re: wait_for_file ?? [who/what/where does fclose()?], (continued)
- Re: wait_for_file ?? [who/what/where does fclose()?], bpabbott, 2010/09/10
- Re: wait_for_file ?? [who/what/where does fclose()?], bpabbott, 2010/09/10
- Re: wait_for_file ?? [who/what/where does fclose()?], Shai Ayal, 2010/09/10
- Re: wait_for_file ?? [who/what/where does fclose()?], Michael D Godfrey, 2010/09/10
- Re: wait_for_file ?? [who/what/where does fclose()?], bpabbott, 2010/09/10
- Re: wait_for_file ?? [who/what/where does fclose()?], Michael D Godfrey, 2010/09/10
- Re: wait_for_file ?? [who/what/where does fclose()?], John W. Eaton, 2010/09/10
- Re: wait_for_file ?? [who/what/where does fclose()?], Michael D Godfrey, 2010/09/10
- Re: wait_for_file ?? [who/what/where does fclose()?],
Shai Ayal <=
- Re: wait_for_file ?? [who/what/where does fclose()?], Michael D Godfrey, 2010/09/10
- Re: wait_for_file ?? [GL2PS error: Bad file pointer], Ben Abbott, 2010/09/11
- Re: wait_for_file ?? [GL2PS error: Bad file pointer], Michael D Godfrey, 2010/09/11
- Re: wait_for_file ?? [GL2PS error: Bad file pointer], Michael D Godfrey, 2010/09/11
- Re: wait_for_file ?? [GL2PS error: Bad file pointer], Shai Ayal, 2010/09/12
- Re: wait_for_file ?? [GL2PS error: Bad file pointer], Michael D Godfrey, 2010/09/12
- Re: wait_for_file ?? [GL2PS error: Bad file pointer], Ben Abbott, 2010/09/12
- Re: wait_for_file ?? [GL2PS error: Bad file pointer], Michael D Godfrey, 2010/09/12
- Re: wait_for_file ?? [GL2PS error: Bad file pointer], Shai Ayal, 2010/09/12
- Re: wait_for_file ?? [GL2PS error: Bad file pointer], Michael D Godfrey, 2010/09/12