linux-kernel - PROBLEM: tickless scheduling

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Date:	Mon, 10 May 2010 20:18:00 -0400
From:	Donald Allen <donaldcallen@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: PROBLEM: tickless scheduling

1. Network file transfers and fscks stop on Toshiba netbook unless
system receives external events
2. I have a new Toshiba NB305 on which I installed the beta release of
Slackware 13.1, which provides a 2.6.33.3 kernel with the tickless
option enabled. With this machine on my ethernet, I attempted to rsync
my home directory to it, about 9 Gb, from a workstation that is my
primary system (running Slackware 13). The transfer proceeded normally
for awhile and then stopped, which I could see in the xterm on the
workstation. I went to the netbook to see what was going on there and
when I began typing, the transfer resumed. I ran 'top' on the netbook
and it would freeze after a few updates, coinciding with the file
transfer pausing again. Typing would get things moving. At another
point, I tested pm-suspend on the netbook. Suspending worked, but
awakening did not, so I had to power-cycle the machine. I use ext2 for
reasons which I won't attempt to justify here, so when the machine
came back up, it fsck'ed the root filesystem. Here again I saw things
grind to a halt -- the progress meter stopped and the there was no
disk activity. But if I moved my finger on the touchpad, things would
get moving again. The only way to get the fsck to complete was to
constantly be tickling the touchpad. I corresponded with Patrick
Volkerding, telling him I suspected a scheduling problem and he
informed me that the 13.1 kernel had tickless enabled, unlike 13. So I
built a 2.6.33.3 kernel (from the Slackware-supplied kernel sources)
with tickless disabled. With that kernel running, I power-cycled the
machine to force a fsck of the root filesystem. This one proceeded to
completion normally -- no external stimuli needed.
3. Tickless, scheduler
4. 2.6.33.3
7.1 ver_linux output attached
7.2 /proc/cpuinfo attached
7.3 /proc/modules attached
7.4 /proc/ioports, /proc/iomem attached
7.5 lspci attached
7.6 /proc/scsi/scsi attached

Download attachment "ver_linux" of type "application/octet-stream" (1414 bytes)

Download attachment "cpuinfo" of type "application/octet-stream" (618 bytes)

Download attachment "modules" of type "application/octet-stream" (2851 bytes)

Download attachment "ioports" of type "application/octet-stream" (1156 bytes)

Download attachment "iomem" of type "application/octet-stream" (1487 bytes)

Download attachment "lspci" of type "application/octet-stream" (22333 bytes)

Download attachment "scsi" of type "application/octet-stream" (336 bytes)