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Re: [PATCH v7 5/6] migration: Reduce time of loading non-iterable vmstat
From: |
Peter Xu |
Subject: |
Re: [PATCH v7 5/6] migration: Reduce time of loading non-iterable vmstate |
Date: |
Fri, 10 Mar 2023 09:58:19 -0500 |
On Fri, Mar 10, 2023 at 10:24:24AM +0800, Chuang Xu wrote:
> The duration of loading non-iterable vmstate accounts for a significant
> portion of downtime (starting with the timestamp of source qemu stop and
> ending with the timestamp of target qemu start). Most of the time is spent
> committing memory region changes repeatedly.
>
> This patch packs all the changes to memory region during the period of
> loading non-iterable vmstate in a single memory transaction. With the
> increase of devices, this patch will greatly improve the performance.
>
> Note that the following test results are based on the application of the
> next patch. Without the next patch, the improvement will be reduced.
>
> Here are the test1 results:
> test info:
> - Host
> - Intel(R) Xeon(R) Platinum 8362 CPU
> - Mellanox Technologies MT28841
> - VM
> - 32 CPUs 128GB RAM VM
> - 8 16-queue vhost-net device
> - 16 4-queue vhost-user-blk device.
>
> time of loading non-iterable vmstate downtime
> before about 112 ms 285 ms
> after about 20 ms 194 ms
>
> In test2, we keep the number of the device the same as test1, reduce the
> number of queues per device:
>
> Here are the test2 results:
> test info:
> - Host
> - Intel(R) Xeon(R) Platinum 8362 CPU
> - Mellanox Technologies MT28841
> - VM
> - 32 CPUs 128GB RAM VM
> - 8 1-queue vhost-net device
> - 16 1-queue vhost-user-blk device.
>
> time of loading non-iterable vmstate downtime
> before about 65 ms about 151 ms
>
> after about 19 ms about 100 ms
>
> In test3, we keep the number of queues per device the same as test1, reduce
> the number of devices:
>
> Here are the test3 results:
> test info:
> - Host
> - Intel(R) Xeon(R) Platinum 8362 CPU
> - Mellanox Technologies MT28841
> - VM
> - 32 CPUs 128GB RAM VM
> - 1 16-queue vhost-net device
> - 1 4-queue vhost-user-blk device.
>
> time of loading non-iterable vmstate downtime
> before about 24 ms about 51 ms
> after about 9 ms about 36 ms
>
> As we can see from the test results above, both the number of queues and
> the number of devices have a great impact on the time of loading non-iterable
> vmstate. The growth of the number of devices and queues will lead to more
> mr commits, and the time consumption caused by the flatview reconstruction
> will also increase.
>
> Signed-off-by: Chuang Xu <xuchuangxclwt@bytedance.com>
> ---
> migration/savevm.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/migration/savevm.c b/migration/savevm.c
> index aa54a67fda..9a7d3e40d6 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2762,6 +2762,7 @@ out:
> goto retry;
> }
> }
> +
Useless line change.
> return ret;
> }
Other than that,
Reviewed-by: Peter Xu <peterx@redhat.com>
--
Peter Xu
- [PATCH v7 1/6] memory: Reference as->current_map directly in memory commit, (continued)
- [PATCH v7 1/6] memory: Reference as->current_map directly in memory commit, Chuang Xu, 2023/03/09
- [PATCH v7 2/6] rcu: Introduce rcu_read_is_locked(), Chuang Xu, 2023/03/09
- [PATCH v7 3/6] memory: Introduce memory_region_transaction_do_commit(), Chuang Xu, 2023/03/09
- [PATCH v7 4/6] memory: Add sanity check in address_space_to_flatview, Chuang Xu, 2023/03/09
- [PATCH v7 5/6] migration: Reduce time of loading non-iterable vmstate, Chuang Xu, 2023/03/09
- [PATCH v7 6/6] memory: Introduce address_space_to_flatview_rcu(), Chuang Xu, 2023/03/09