On Jan 10, 2008 6:50 AM, Shreyansh <shreyansh.jain@xxxxxxxxx> wrote: > Hi All, > > While working (debugging) on one of my kernel modules (a file system), > I had to put a lot of printk to understand and track all the changes that > were happening. These printk had variables being printed and sometimes > in loop. In essence, there was a huge log generated even for a small I/O. > > I also noticed that sometimes (not always but not rare as well) the > /var/log/messages file had grabled text. Part of the text which belonged > to the thrown printk was corrupted. Besides the order of printk being > jumbled, the data which was being printed was also corrupted (with special > characters). > > Also, when I reduced the number of printk (switching off a macro), I found > this problem appearing even lesser. And infact, I could not reproduce this > problem when I had just 10-20 lines of printk per module call. > > What I am wondering is that is it possible that excessive use of printk is > causing corruption of the printk log buffer? Any hints/pointers as to what > should I do to debug this kind of problem? > > I am currently working on SLES 10 SP1 (2.6.16.46 kernel) on an SMP opteron > machine. > > Thanks, > > Shreyansh Shreyansh, As a general the output of dmesg is higher quality than /var/log/messages. Dmesg directly accesses the kernel's memory based log buffer. If you want to have a high quality copy of the messages on disk, then make your own copy. ie. "dmesg > my-dmesg-copy" The negative with dmesg is that the kernel's buffer is a fifo. If for some reason it is too small for the amount of logging you need, then you can adjust the size and make as big as you need. Greg -- Greg Freemyer Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer First 99 Days Litigation White Paper - http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
