On Fri, Sep 21, 2012 at 09:23:57AM +0900, HATAYAMA Daisuke wrote: > From: Vivek Goyal <vgoyal at redhat.com> > Subject: makedumpfile 1.5.0 takes much more time to dump > Date: Thu, 20 Sep 2012 16:06:34 -0400 > > > Hi Atsushi san, > > > > We tried makedumpfile 1.5.0 on a 1TB machine and it seems to regress > > badly. We reserved 192MB of memory and following are test results. > > > > #1. makedumpfile-1.4.2 -E --message-level 1 -d 31 > > real 3m47.520s > > user 0m56.543s > > sys 2m41.631s > > > > #2. makedumpfile-1.5.0 -E --message-level 1 -d 31 > > real 52m25.262s > > user 32m51.310s > > sys 18m53.265s > > > > #3. makedumpfile-1.4.2 -c --message-level 1 -d 31 > > real 8m49.107s > > user 4m34.180s > > sys 4m8.691s > > > > #4. makedumpfile-1.5.0 -c --message-level 1 -d 31 > > real 46m48.985s > > user 29m35.203s > > sys 16m43.149s > > > > Hello Vivek, > > On v1.5.0 we cannot filter free pages in constant space becuase we > have yet to test it. Instead, the existing method is used here, which > repeats walking on a whole page frames the number of cycles times. > > As Kumagai-san explains, the number of cycles can be calculated by the > following expression: > > N = physical memory size / (page size * bit per byte(8) * BUFSIZE_CYCLIC) > > So, > > N = 2TB / (4KB * 8 * 1MB) = 64 cycles. > > I guess on this environment, it took about 50 seconds to filter free > pages in one cycle. Ok, so once we have your walking through page struct patches in, hopefully this problem will be gone? If that's going to take time, can we make using of new logic conditional on a command line option. So that user has the option of using old logic. Thanks Vivek
