From: Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Peter Xu <peterx@redhat.com>
Cc: Peter Krempa <pkrempa@redhat.com>,
qemu-devel@nongnu.org, Den Lunev <den@openvz.org>,
Eric Blake <eblake@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Juan Quintela <quintela@redhat.com>,
Markus Armbruster <armbru@redhat.com>
Subject: Re: [PATCH v4 0/6] UFFD write-tracking migration/snapshots
Date: Tue, 1 Dec 2020 23:29:00 +0300 [thread overview]
Message-ID: <5b7a5ad4-c722-3261-8784-97972d9923bd@virtuozzo.com> (raw)
In-Reply-To: <20201201200137.GQ4338@work-vm>
On 01.12.2020 23:01, Dr. David Alan Gilbert wrote:
> * Peter Xu (peterx@redhat.com) wrote:
>> On Tue, Dec 01, 2020 at 06:40:55PM +0000, Dr. David Alan Gilbert wrote:
>>>> Yep, seems that current userfaultfd supports hugetlbfs and shared memory for
>>>> missing pages but not for wr-protected..
>>>
>>> For hugepages, you'd need kernel support - but also you'd want to make
>>> sure you write the whole hugepage at once.
>>
>> Or we can do similar things by splitting the huge pages just like when we
>> migrate.
>>
>> I should have overlooked these facts when I replied previusly - we do need the
>> same logic, but also special care on these special memory types.
>>
>>>
>>> For shared, there's a harder problem to ask; what happens if RAM is
>>> written by the other process - for postcopy, we get the other process
>>> to send us a userfaultfd that they have registered with their VM.
>>
>> Good point... so we should need similar things too.
>>
>> Looks like we'd better explicitly disable shmem/hugetlbfs for now from qemu
>> background snapshots before we have prepared these utilities, just in case it
>> got run on some "future" kernels and accidentally got enabled, so the snapshot
>> files could be corrupted ones.
>>
>> Is shmem used a lot in libvirt, or is it even a default configuration?
>
> No, but it's used with vhost-user applications; like dpdk.
>
> Dave
>
>> --
>> Peter Xu
>>
Yep.
--
Andrey Gruzdev, Principal Engineer
Virtuozzo GmbH +7-903-247-6397
virtuzzo.com
next prev parent reply other threads:[~2020-12-01 20:36 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-26 15:17 [PATCH v4 0/6] UFFD write-tracking migration/snapshots Andrey Gruzdev via
2020-11-26 15:17 ` [PATCH v4 1/6] introduce 'background-snapshot' migration capability Andrey Gruzdev via
2020-11-27 19:55 ` Peter Xu
2020-11-28 16:35 ` Andrey Gruzdev
2020-11-26 15:17 ` [PATCH v4 2/6] introduce UFFD-WP low-level interface helpers Andrey Gruzdev via
2020-11-27 21:04 ` Peter Xu
2020-11-29 20:12 ` Andrey Gruzdev
2020-11-30 15:34 ` Peter Xu
2020-11-30 18:41 ` Andrey Gruzdev
2020-12-01 12:24 ` Dr. David Alan Gilbert
2020-12-01 19:32 ` Andrey Gruzdev
2020-11-26 15:17 ` [PATCH v4 3/6] support UFFD write fault processing in ram_save_iterate() Andrey Gruzdev via
2020-11-27 21:49 ` Peter Xu
2020-11-29 21:14 ` Andrey Gruzdev
2020-11-30 16:32 ` Peter Xu
2020-11-30 19:27 ` Andrey Gruzdev
2020-11-26 15:17 ` [PATCH v4 4/6] implementation of background snapshot thread Andrey Gruzdev via
2020-11-26 15:17 ` [PATCH v4 5/6] the rest of write tracking migration code Andrey Gruzdev via
2020-11-27 22:26 ` Peter Xu
2020-11-30 8:09 ` Andrey Gruzdev
2020-11-26 15:17 ` [PATCH v4 6/6] introduce simple linear scan rate limiting mechanism Andrey Gruzdev via
2020-11-27 22:28 ` Peter Xu
2020-11-30 8:11 ` Andrey Gruzdev
2020-11-30 16:40 ` Peter Xu
2020-11-30 19:30 ` Andrey Gruzdev
2020-11-26 15:47 ` [PATCH v4 0/6] UFFD write-tracking migration/snapshots Peter Krempa
2020-11-27 8:21 ` Andrey Gruzdev
2020-11-27 9:49 ` Peter Krempa
2020-11-27 10:00 ` Andrey Gruzdev
2020-11-27 15:45 ` Peter Xu
2020-11-27 17:19 ` Andrey Gruzdev
2020-11-27 22:04 ` Peter Xu
2020-11-30 8:07 ` Andrey Gruzdev
2020-12-01 7:08 ` Peter Krempa
2020-12-01 8:42 ` Andrey Gruzdev
2020-12-01 10:53 ` Peter Krempa
2020-12-01 11:24 ` Andrey Gruzdev
2020-12-01 18:40 ` Dr. David Alan Gilbert
2020-12-01 19:22 ` Peter Xu
2020-12-01 20:01 ` Dr. David Alan Gilbert
2020-12-01 20:29 ` Andrey Gruzdev [this message]
2020-12-01 20:11 ` Andrey Gruzdev
2020-12-01 18:54 ` Peter Xu
2020-12-01 20:00 ` Dr. David Alan Gilbert
2020-12-01 20:26 ` Andrey Gruzdev
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