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Re: [Qemu-devel] [PATCH v2 16/16] postcopy: Add doc about hugepages and
From: |
Laurent Vivier |
Subject: |
Re: [Qemu-devel] [PATCH v2 16/16] postcopy: Add doc about hugepages and postcopy |
Date: |
Fri, 24 Feb 2017 17:12:52 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 |
On 06/02/2017 18:33, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
> docs/migration.txt | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/docs/migration.txt b/docs/migration.txt
> index 6503c17..b462ead 100644
> --- a/docs/migration.txt
> +++ b/docs/migration.txt
> @@ -482,3 +482,16 @@ request for a page that has already been sent is
> ignored. Duplicate requests
> such as this can happen as a page is sent at about the same time the
> destination accesses it.
>
> +=== Postcopy with hugepages ===
> +
> +Postcopy now works with hugetlbfs backed memory:
> + a) The linux kernel on the destination must support userfault on hugepages.
> + b) The huge-page configuration on the source and destination VMs must be
> + identical; i.e. RAMBlocks on both sides must use the same page size.
> + c) Note that -mem-path /dev/hugepages will fall back to allocating normal
> + RAM if it doesn't have enough hugepages, triggering (b) to fail.
> + Using -mem-prealloc enforces the allocation using hugepages.
> + d) Care should be taken with the size of hugepage used; postcopy with 2MB
> + hugepages works well, however 1GB hugepages are likely to be problematic
> + since it takes ~1 second to transfer a 1GB hugepage across a 10Gbps
> link,
> + and until the full page is transferred the destination thread is
> blocked.
>
Reviewed-by: Laurent Vivier <address@hidden>
- Re: [Qemu-devel] [PATCH v2 08/16] postcopy: Plumb pagesize down into place helpers, (continued)
- [Qemu-devel] [PATCH v2 13/16] postcopy: Allow hugepages, Dr. David Alan Gilbert (git), 2017/02/06
- [Qemu-devel] [PATCH v2 14/16] postcopy: Update userfaultfd.h header, Dr. David Alan Gilbert (git), 2017/02/06
- [Qemu-devel] [PATCH v2 12/16] postcopy: Send whole huge pages, Dr. David Alan Gilbert (git), 2017/02/06
- [Qemu-devel] [PATCH v2 16/16] postcopy: Add doc about hugepages and postcopy, Dr. David Alan Gilbert (git), 2017/02/06
- [Qemu-devel] [PATCH v2 10/16] postcopy: Load huge pages in one go, Dr. David Alan Gilbert (git), 2017/02/06
- [Qemu-devel] [PATCH v2 15/16] postcopy: Check for userfault+hugepage feature, Dr. David Alan Gilbert (git), 2017/02/06
- Re: [Qemu-devel] [PATCH v2 00/16] Postcopy: Hugepage support, Dr. David Alan Gilbert, 2017/02/06