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Thu, 5 Dec 2019 13:54:39 +0000 (UTC) Received: from redhat.com (ovpn-117-232.ams2.redhat.com [10.36.117.232]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1DF9D6B8D5; Thu, 5 Dec 2019 13:54:34 +0000 (UTC) From: Juan Quintela To: "Dr. David Alan Gilbert \(git\)" Subject: Re: [PATCH] migration: Rate limit inside host pages In-Reply-To: <20191205102918.63294-1-dgilbert@redhat.com> (David Alan Gilbert's message of "Thu, 5 Dec 2019 10:29:18 +0000") References: <20191205102918.63294-1-dgilbert@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) Date: Thu, 05 Dec 2019 14:54:31 +0100 Message-ID: <87o8wmkhd4.fsf@trasno.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: yuMmZ7P-PtK6Uq2gIeDTSg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: quintela@redhat.com Cc: qemu-devel@nongnu.org, peterx@redhat.com, LMa@suse.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" "Dr. David Alan Gilbert (git)" wrote: > From: "Dr. David Alan Gilbert" > > 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 > Signed-off-by: Dr. David Alan Gilbert > --- Reviewed-by: Juan Quintela 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, PageSea= rchStatus *pss, > =20 > pages +=3D 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_BIT= S)); > =20 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.