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Re: [PATCH] migration: Rate limit inside host pages
From: |
Juan Quintela |
Subject: |
Re: [PATCH] migration: Rate limit inside host pages |
Date: |
Thu, 05 Dec 2019 14:54:31 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) |
"Dr. David Alan Gilbert (git)" <address@hidden> wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> When using hugepages, rate limiting is necessary within each huge
> page, since a 1G huge page can take a significant time to send, so
> you end up with bursty behaviour.
>
> Fixes: 4c011c37ecb3 ("postcopy: Send whole huge pages")
> Reported-by: Lin Ma <address@hidden>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
Reviewed-by: Juan Quintela <address@hidden>
I can agree that rate limit needs to be done for huge pages.
> diff --git a/migration/ram.c b/migration/ram.c
> index a4ae3b3120..a9177c6a24 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2616,6 +2616,8 @@ static int ram_save_host_page(RAMState *rs,
> PageSearchStatus *pss,
>
> pages += tmppages;
> pss->page++;
> + /* Allow rate limiting to happen in the middle of huge pages */
> + migration_rate_limit();
> } while ((pss->page & (pagesize_bits - 1)) &&
> offset_in_ramblock(pss->block, pss->page << TARGET_PAGE_BITS));
>
But is doing the rate limit for each page, no? Even when not using huge
pages.
Not that it should be a big issue (performance wise).
Have you done any meassuremnet?
Later, Juan.