From: Cliff Wickman <cpw@xxxxxxx> Subject: Re: [PATCH v2] makedumpfile: request the kernel do page scans Date: Mon, 7 Jan 2013 07:39:35 -0600 > An update on testing thise patches: > >> This version of the patch improves the consolidation of the mem_map table >> that is passed to the kernel. See make_kernel_mmap(). >> Particularly the seemingly duplicate pfn ranges generated on an older >> (2.6.32-based, rhel6) kernel. > > > On a 2TB machine (idle) machine: > the crash kernel ran successfully in 512M > the scan for unnecessary pages takes about 40 seconds > it was a single scan, not cyclic > > On a 16TB machine (idle) machine: > the crash kernel ran successfully in 512M > there is a pause of about 4 minutes during makedumpfile initialization > the scan for unnecessary pages takes about 4.8 minutes > it was a single scan, not cyclic > I wonder why this didn't result in OOM on 16TB. Was that really done in non-cyclic mode? Could you show me a log of makedumpfile? You can create it by passing --message-level 31. Also, to consider how to resolve this performance issue, this test is not enough. We also need to benchmark that *without filtering in kernel-space* but with making page tables, not using ioremap. As I said before, I think the bad performance is caused by too many calls of ioremap/iounmap. We then need to comapre two results of these benchmarks. Thanks. HATAYAMA, Daisuke
