Re: [OT] Mail hangs real-time processes
Re: [OT] Mail hangs real-time processes
- Subject: Re: [OT] Mail hangs real-time processes
- From: Jens Bauer <email@hidden>
- Date: Wed, 7 Jan 2004 06:00:55 +0100
Hi Jeff,
[Sorry, in my last reply, I forgot to choose the right reply-account,
so the message wasn't copied to the list]
On Wednesday, Jan 7, 2004, at 01:12 Europe/Copenhagen, Jeff Moore wrote:
Before, I get into this, I remembered one other question that would be
helpful to know the answer to: When the hang happens, does the mouse
move normally? That is, does it stutter around or move smoothly like
normal?
At my place, I can still move the mouse.
At any rate, 50000+ messages in one folder is probably on the large
side for mail folders. Opening one is going to cause a massive amount
of disk IO and possibly a fair amount of VM paging, especially given
the amount of RAM you have. Indeed, using fs_usage I see all sorts of
disk activity going on when I open one of my own small mail folders. I
don't see any VM activity, but my mailbox is small (and nobody in my
immediate vicinity had one any where near that big) so probably won't
have the same memory behavior.
Just in case anyone is wondering why I have that many msgs; it's the
CocoaDev list, and I like to use it for answering dev questions
quickly. ;)
So, it could be that VM paging or Mail's disk IO is preventing iTunes
from getting at the audio data on the disk when it needs it. VM paging
would be the worst since it will additionally hold off the HAL's IO
thread which will cause glitches.
It's possible, that this is what happened. It's a long glitch. (not
"skips", nor "mutes", because it played from where it left; I
experienced "mutes" with MacAMP once a day, these mutes were for 3
seconds, but that's a completely different story).
So to see if the disk activity is causing troubles, I'd do the
following:
1) Shutdown the machine and cold boot it. Cold booting makes sure that
as little stuff is cached or otherwise already loaded as possible
which should exacerbate this problem if it is disk related.
2) Play back some audio using a tool that does all it's work directly
out of RAM, like HALLab. QTPlayer, iTunes, and most others buffer the
file data off the disk as needed so aren't suitable for this test.
You mean something like a tone-generator application ? I could write
one for that purpose, yes.
3) Launch Mail and open the big mail folder and see if it interrupts
the playback.
It might be helpful to run fs_usage as well in a shell somewhere so
you can see who's doing what sort of disk IO.
Would it be best to run this app via the network, or locally?
For the record:
Sample(1) is a command line tool that can take a peak at the stacks of
all the threads in a process over time. It is a great tool for
diagnosing hangs, infinite loops, and other issues that can be seen
from a stack crawl.
Heh, OK, I was confused because of the name; speaking about audio, and
taking samples didn't make me think of the sampler. =)
The man page is probably the best documentation for it. While I find
the command line version the easiest to use, there is also a GUI
version called Sampler which is located in
/Developer/Applications/Performance Tools. I think the docs that
discuss the various performance tools also has some info on the GUI
version. Now that we have a bit more detail, a sample trace probably
won't be all that easy to get for the portion of time that it is
needed since the hang is so brief.
I can try and see if I can get it anyway. It's worth the try, if I
succeed. ;)
Love,
Jens
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