From: Juan Quintela <quintela@redhat.com>
To: "Dr. David Alan Gilbert \(git\)" <dgilbert@redhat.com>
Cc: qemu-devel@nongnu.org, peterx@redhat.com, LMa@suse.com
Subject: Re: [PATCH] migration: Rate limit inside host pages
Date: Thu, 05 Dec 2019 14:54:31 +0100 [thread overview]
Message-ID: <87o8wmkhd4.fsf@trasno.org> (raw)
In-Reply-To: <20191205102918.63294-1-dgilbert@redhat.com> (David Alan Gilbert's message of "Thu, 5 Dec 2019 10:29:18 +0000")
"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> 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 <LMa@suse.com>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
Reviewed-by: Juan Quintela <quintela@redhat.com>
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.
next prev parent reply other threads:[~2019-12-05 13:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-05 10:29 [PATCH] migration: Rate limit inside host pages Dr. David Alan Gilbert (git)
2019-12-05 13:54 ` Juan Quintela [this message]
2019-12-05 14:30 ` Dr. David Alan Gilbert
2019-12-05 13:55 ` Peter Xu
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