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From: | Chegu Vinod |
Subject: | Re: [Qemu-devel] [PATCH v4] Add option to mlock qemu and guest memory |
Date: | Sun, 21 Apr 2013 22:16:26 -0700 |
User-agent: | Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 |
Hi Satoru,FYI... I had tried to use this change earlier and it did show some improvements in perf. (due to reduced exits).
But as expected mlockall () on large sized guests adds a considerable delay in boot time. For e.g. on an 8 socket Westmere box => a 256G guest : took an additional ~2+ mins to boot and a 512G guest took an additional ~5+ mins to boot. This is mainly due to long time spent in trying to clear all the pages.
77.96% 35728 qemu-system-x86 [kernel.kallsyms] [k] clear_page_c
| --- clear_page_c hugetlb_no_page hugetlb_fault follow_hugetlb_page __get_user_pages __mlock_vma_pages_range __mm_populate vm_mmap_pgoff sys_mmap_pgoff sys_mmap system_call __GI___mmap64 qemu_ram_alloc_from_ptr qemu_ram_alloc memory_region_init_ram pc_memory_init pc_init1 pc_init_pci main __libc_start_main Need to have a faster way to clear pages. Vinod
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