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Re: [Qemu-devel] [PATCH v4] Add option to mlock qemu and guest memory
From: |
Satoru Moriya |
Subject: |
Re: [Qemu-devel] [PATCH v4] Add option to mlock qemu and guest memory |
Date: |
Tue, 23 Apr 2013 12:47:25 +0900 |
User-agent: |
Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 |
Hi Vinod,
Thank you for your report.
(2013/04/22 14:16), Chegu Vinod wrote:
> 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.
Yes, it is expected.
> 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.
Hmm, clear_page() just calls memset(page, 0, PAGE_SIZE)...
The patch has just merged today. I'll start to think of the issue above.
Regards,
Satoru