| Message ID | 20230310022425.2992472-6-xuchuangxclwt@bytedance.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | migration: reduce time of loading non-iterable vmstate | expand |
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>
Chuang Xu <xuchuangxclwt@bytedance.com> 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; > } > } > + > return ret; > } > Drop this. > @@ -2787,7 +2788,25 @@ int qemu_loadvm_state(QEMUFile *f) > > cpu_synchronize_all_pre_loadvm(); > > + /* > + * Call memory_region_transaction_begin() before loading vmstate. > + * This call is paired with memory_region_transaction_commit() at > + * the end of qemu_loadvm_state_main(), in order to pack all the > + * changes to memory region during the period of loading > + * non-iterable vmstate in a single memory transaction. > + * This operation will reduce time of loading non-iterable vmstate > + */ > + memory_region_transaction_begin(); > + > ret = qemu_loadvm_state_main(f, mis); > + > + /* > + * Call memory_region_transaction_commit() after loading vmstate. > + * At this point, qemu actually completes all the previous memory > + * region transactions. > + */ > + memory_region_transaction_commit(); > + > qemu_event_set(&mis->main_thread_load_event); > > trace_qemu_loadvm_state_post_main(ret); Reviewed-by: Juan Quintela <quintela@redhat.com> I don't feel confident getting this series through the migration tree without Paolo (or someone else more familiar with the memory API) reviews it. So if anyone else reviews it, I will got it through the migration tree, otherwise I am ok to have it pulled trhough other tree. Not sure if we should get this in the middle of the freeze or should we wait for 8.1 to open.
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; } } + return ret; } @@ -2787,7 +2788,25 @@ int qemu_loadvm_state(QEMUFile *f) cpu_synchronize_all_pre_loadvm(); + /* + * Call memory_region_transaction_begin() before loading vmstate. + * This call is paired with memory_region_transaction_commit() at + * the end of qemu_loadvm_state_main(), in order to pack all the + * changes to memory region during the period of loading + * non-iterable vmstate in a single memory transaction. + * This operation will reduce time of loading non-iterable vmstate + */ + memory_region_transaction_begin(); + ret = qemu_loadvm_state_main(f, mis); + + /* + * Call memory_region_transaction_commit() after loading vmstate. + * At this point, qemu actually completes all the previous memory + * region transactions. + */ + memory_region_transaction_commit(); + qemu_event_set(&mis->main_thread_load_event); trace_qemu_loadvm_state_post_main(ret);
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(+)