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Date: Sun, 21 Apr 2013 22:16:26 -0700
From: Chegu Vinod <chegu_vinod@hp.com>
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Subject: Re: [Qemu-devel] [PATCH v4] Add option to mlock qemu and guest
	memory
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To: Satoru Moriya <satoru.moriya@hds.com>, qemu-devel qemu-devel <qemu-devel@nongnu.org>

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