From: Vivek Goyal <vgoyal@xxxxxxxxxx> 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. Thanks. HATAYAMA, Daisuke