From: ezyang@MIT.EDU (Edward Z. Yang)
Subject: [sup-talk] Sup is hanging
Date: Wed, 3 Jun 2009 17:48:56 -0400 (EDT) [thread overview]
Message-ID: <alpine.DEB.2.00.0906031740370.22220@javelin> (raw)
In-Reply-To: <1244064889-sup-9506@entry>
On Wed, 3 Jun 2009, William Morgan wrote:
> Reformatted excerpts from Edward Z. Yang's message of 2009-06-03:
>> The current working theory (based on strace'ing and lsof) is that Sup
>> is hanging on a select() call that doesn't have any timeout. The
>> reason why this is hanging is because between opening the connection
>> and closing it, Sup does some ridiculously slow message parsing code
>> (that really thrashes the CPU) and by the time it's done the server
>> has closed the connection (but we don't know about it).
>
> That may all be true, but I'd be surprised if a) Sup didn't know that
> the server had closed the connection, and
It doesn't have anything to do with Sup: the system select() call is
hanging; Sup (and Ruby for that matter) is out of the equation. This
might be IMAP server weirdness, but that shouldn't cause Sup to
freeze.
> b) that this would cause the
> whole thing to hang.
That's what I find surprising, since Sup is multithreaded. I suppose
all of the threads are blocking on the select.
Sup hangs without -n. (it always hangs after it's "done fetching IMAP
headers"). "done fetching IMAP headers" is the last message we get.
The behavior seems to be:
1. Log reports "done fetching IMAP headers"
2. Sup begins malloc'ing like crazy. sup-sync still is able to catch
signals and if you kill it you find that it's somewhere in
lib/sup/message.rb, message_to_chunks. sup doesn't respond to Ctrl+C
3. After some minutes, CPU usage dies off, but Sup doesn't unfreeze.
strace indicates that sup/sup-sync is waiting on a select(), and that
the descriptors are TCP connections to the IMAP server.
Cheers,
Edward
next prev parent reply other threads:[~2009-06-03 21:48 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-03 17:39 Edward Z. Yang
2009-06-03 18:11 ` William Morgan
2009-06-03 18:26 ` Edward Z. Yang
2009-06-03 18:21 ` Edward Z. Yang
2009-06-03 18:45 ` Edward Z. Yang
2009-06-03 21:36 ` William Morgan
2009-06-03 21:48 ` Edward Z. Yang [this message]
2009-06-04 2:11 ` William Morgan
2009-06-03 22:00 ` [sup-talk] Sup is hangingy Edward Z. Yang
2009-06-04 1:26 ` Edward Z. Yang
2009-06-04 1:53 ` [sup-talk] Sup is hangingyy Edward Z. Yang
2009-06-04 16:09 ` [sup-talk] Sup is hanging William Morgan
2009-06-05 5:08 ` Edward Z. Yang
2009-06-05 13:23 ` William Morgan
[not found] ` <1244227108-sup-3123@cabinet>
2009-06-05 21:47 ` Edward Z. Yang
2009-06-06 6:20 ` Edward Z. Yang
2009-06-08 18:09 ` William Morgan
2009-06-04 2:12 ` [sup-talk] Sup is hangingy William Morgan
2009-06-04 2:13 ` William Morgan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.00.0906031740370.22220@javelin \
--to=ezyang@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox