On 03/08/2013 11:52 PM, Vivek Goyal wrote: > On Thu, Mar 07, 2013 at 01:54:45PM -0800, Eric W. Biederman wrote: >> Vivek Goyal<vgoyal at redhat.com> writes: >> >>> On Thu, Mar 07, 2013 at 10:58:18PM +0800, Jingbai Ma wrote: >>>> This patch intend to speedup the memory pages scanning process in >>>> selective dump mode. >>>> >>>> Test result (On HP ProLiant DL980 G7 with 1TB RAM, makedumpfile >>>> v1.5.3): >>>> >>>> Total scan Time >>>> Original kernel >>>> + makedumpfile v1.5.3 cyclic mode 1958.05 seconds >>>> Original kernel >>>> + makedumpfile v1.5.3 non-cyclic mode 1151.50 seconds >>>> Patched kernel >>>> + patched makedumpfile v1.5.3 17.50 seconds >>>> >>>> Traditionally, to reduce the size of dump file, dumper scans all memory >>>> pages to exclude the unnecessary memory pages after capture kernel >>>> booted, and scan it in userspace code (makedumpfile). >>> >>> I think this is not a good idea. It has several issues. >> >> Actually it does not appear to be doing any work in the first kernel. > > Looks like patch3 in series is doing that. > > machine_crash_shutdown(&fixed_regs); > + generate_crash_dump_bitmap(); > machine_kexec(kexec_crash_image); > > So this bitmap seems to be being set just before transitioning into > second kernel. > > I am sure you would not like this extra code in this path. :-) I was thought this function code is pretty simple, could be called here safely. If it's not proper for here, how about before the function machine_crash_shutdown(&fixed_regs)? Furthermore, could you explain the real risks to execute more codes here? Thanks! > > Thanks > Vivek -- Jingbai Ma (jingbai.ma at hp.com)
