Re: [Pan-users] Inefficiencies in Pan threading?

[Calin A. Culianu]

On Sat, 13 Sep 2003, Wolf J. Flywheel wrote:

> On Saturday 13 September 2003 21:05, Calin A. Culianu wrote:
>
> > downloading binary attachements.  Namely, I have a queue of tens of
> > megabytes worth of attachements in my task list, but Pan is only using
> > 1 thread at a time to download these binaries (I specified a connection
> > limit of 4 in the server config UI).  This doesn't sound so bad,
>
>       I'm sure I won't be the only one to bring this up, but behind the scenes
> Pan actually *is* using all 4 connections.  (Well, it should be... do you
> have a bandwidth monitor such as gkrellm?  That should show you.)  A few
> revisions ago, the behavior was changed from grabbing chunks of 4
> different binaries concurrently to grabbing 4 chunks of the same one.
> However, since it's only working on one "thing" at a time, you'll only
> see one item in the status bar.  You may notice more there if it's near
> the end of one, and therefore it's waiting for one or more threads to
> finish working on #1, but other threads have moved on to #2.
>
>       BTW, the extreme lower left of Pan's window shows the number of tasks; 
> it
> should look like "3 @ 150.2 KB/s" or such while things are downloading.
> That's saying, "I have 3 connections going, and together they're using
> 150.2 KB per second."
>
>       I hope this was helpful in some way.  :)  For way more info than you
> need, see /usr/share/doc/pan-0.14.2/ChangeLog.gz -- discussion of this
> business takes place around line 2358.  (Oh, I see you're on 0.14.0...
> not sure where it would be in that changelog, but search for
> "pan/task-state.[ch]: new object.  This object is used by tasks".  0.14.2
> is in Portage now, though!)
>
>

Mr. Flywheel,

Many thanks for your detailed explanation.  My mind is at ease now that I
know Pan is 'doing the right thing' and gobbling up as many connections to
the news server as are permitted.

I personally think that Pan should be more arrogant about its connection
usage... it should show off more the fact that it's using many, many
connections (even if they are all on parts of the same file).  This would
give the user a real sense of power.. I may not be the first to have
misintepreted the metrics it prints at the bottom of the window.. :)

By the way, I really like the fact that Pan seems to prioritize user
interactions with the news server over download traffic.  Namely, if I
want to grab a list of article headers, it queues these up ahead of any
downloads, so that the next chance it gets, Pan downloads the headers
immediately. Other newsreader programs seem to get this wrong and force
the user to manually wrestle with his task queue if he wants the headers
right away.. :).

I am still a little puzzled by the sporadic delays and stalls I get while
downloading from my news server.  I previously thought this was dead time
Pan was spending decoding downloaded chunks, but perhaps it is caused by
something else outside of Pan (such as the news server itself).  From your
description it sounds like Pan may not be the source of the delay -- it is
after all trying to minimize "dead time" by interleaving downloading with
decoding.. is this a correct assessment?

Would you have any insights into how I can prevent the stalling I am
seeing?  Or should I look outside of Pan altogether to solve the problem
(like maybe my news server is being slow sporadically..)?

Thanks and much appreciated,

-Calin