extremely slow shell starts (trying to debug, dbus related)

[Cameron Simpson]

On 30Dec2014 08:36, Neal Becker <ndbecker2 at gmail.com> wrote:
>On my server, after updating f20->f21, shell startup is _extremely_ slow.
>
>Using strace, it appears that the problem is dbus
>
>08:22:57 connect(5, {sa_family=AF_LOCAL,
>sun_path="/var/run/dbus/system_bus_socket"}, 33) = 0
>...
>08:22:57 recvmsg(5, 0x7fff640c3970, MSG_CMSG_CLOEXEC) = -1 EAGAIN (Resource
>temporarily unavailable)
>08:22:57 poll([{fd=5, events=POLLIN}], 1, 25000) = 1 ([{fd=5, revents=POLLIN}])
>08:23:22 recvmsg(5, {msg_name(0)=NULL,
>msg_iov(1)=[{"l\3\1\0013\0\0\0\4\0\0\0m\0\0\0\6\1s\0\7\0\0\0:1.1155\0"...,
>2048}], msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 179
>08:23:22 write(6, "\1\0\0\0\0\0\0\0", 8) = 8
>
>Notice the 30second wait for a response from dbus?
>
>Also in /var/log/messages, various dbus messages such as:
>Dec 30 08:19:32 nbecker7 su: (to root) nbecker on pts/0
>Dec 30 08:20:02 nbecker7 dbus[809]: [system] Connection has not authenticated
>soon enough, closing it (auth_timeout=30000ms, elapsed: 30004ms)
>
>Any hints?

Those log line times don't match the strace times. But I'll assume they're 
typical, and associate with your shell startups timingwise.

A few questions:

- why does the shell use dbus at all? (just wondering, I'm presuming this is some bash feature new to me)

- can you strace dbus (pid 809 in the above log)? using strace's -f option if dbus forks.

- 30s is in my head as a standard DNS timeout, but it is also common to some 
other things and your sample strace above shows only 25s. (Though I notice also 
that the timeout in the poll() call is itself exactly 25s).

So you're not seeing a 25s wait before dbus replies, you're seeing a 25s 
timeout on the client (your shell?)?

I'd be trying 2 things: see if dbus has a config option to turn up its 
debugging messages, and strace dbus around a shell start. Eg:

  strace -p 809 -f -o strace.dbus.out

Disclaimer: not running Fedora here, so this is all general advice.

Cheers,
Cameron Simpson <cs at zip.com.au>

  They utter mere words; with empty oaths they make promises; so lawsuits
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Sounds like 20th-century USA, doesn't it? This is from the book of Hosea,
chapter 10, the 4th verse. It's only a few thousand years old...
        - Dan Nitschke <elvis at RedBrick.COM>