Bug 1067188

Description of problem:
By default retrace-server runs makedumpfile on all vmcores which come in based on a variable inside retrace-server.conf, VmcoreDumpLevel.  The idea is to strip out pages to save space and performance (for example, zero pages).  Note that on our server we have this inside /etc/retrace-server.conf:
# Run makedumpfile with specified dumplevel; <= 0 or >= 32 means disabled
VmcoreDumpLevel = 1

However a lot of vmcores which come in already have zero-pages stripped, so running it again by default is extra overhead with no benefit.

We should be able to detect this with a simple heuristic as outlined here (from Marc Milgram)
https://access.redhat.com/site/solutions/696803

I tested on a RHEL5.7 and RHEL6.2 vmcore and both worked great:

[dwysocha@optimus expect]$ ln -s /cores/retrace/tasks/644405833/crash/vmcore test/rhel5.7-vmcore
[dwysocha@optimus expect]$ makedumpfile -D --dump-dmesg test/rhel5.7-vmcore /dev/null 2>/dev/null | grep dump_level
  dump_level       : 1
[dwysocha@optimus expect]$ ln -s /cores/retrace/tasks/645955026/crash/vmcore test/rhel6.2-vmcore
[dwysocha@optimus expect]$ makedumpfile -D --dump-dmesg test/rhel6.2-vmcore /dev/null 2>/dev/null | grep dump_level
  dump_level       : 31

Version-Release number of selected component (if applicable):
retrace-server-1.10-1.el6.noarch
kexec-tools-2.0.0-258.el6_4.2.x86_64

Actual results:
makedumpfile is run on every vmcore based on setting in retrace-server.conf

Expected results:
There should be an option to configure retrace server to not run makedumpfile with redundant options, though I'm not entirely sure of the design.


Additional info:
We probably just need to patch this code in download_remote which calls strip_vmcore in /usr/lib/python2.6/site-packages/retrace/retrace.py

Maybe add a new function to determine dump level of the vmcore?  Then looks like we'll need to do something with VmcoreDumpLevel from the config file, or perhaps add a new config variable.  


def strip_vmcore(vmcore, kernelver=None):
    try:
        vmlinux = prepare_debuginfo(vmcore, kernelver=kernelver)
    except Exception as ex:
        log_warn("prepare_debuginfo failed: %s" % ex)
        return

    newvmcore = "%s.stripped" % vmcore
    retcode = call(["makedumpfile", "-c", "-d", "%d" % CONFIG["VmcoreDumpLevel"],
                    "-x", vmlinux, "--message-level", "0", vmcore, newvmcore])
    if retcode:
        log_warn("makedumpfile exited with %d" % retcode)
        if os.path.isfile(newvmcore):
            os.unlink(newvmcore)
    else:
        os.rename(newvmcore, vmcore)



    def download_remote(self, unpack=True, timeout=0, kernelver=None):
        """Downloads all remote resources and returns a list of errors."""
...
            if os.path.isfile(vmcore):
                oldsize = os.path.getsize(vmcore)
                log_info("Vmcore size: %s" % human_readable_size(oldsize))
                if CONFIG["VmcoreDumpLevel"] > 0 and CONFIG["VmcoreDumpLevel"] < 32:
                    log_debug("Executing makedumpfile")
                    start = time.time()
                    strip_vmcore(vmcore, kernelver)
                    dur = int(time.time() - start)
                    st = os.stat(vmcore)
                    os.chmod(vmcore, st.st_mode | stat.S_IRGRP)
                    log_info("Stripped size: %s" % human_readable_size(st.st_size))
                    log_info("Makedumpfile took %d seconds and saved %s" % (dur, human_readable_size(oldsize - st.st_size)))