On 11/30/23 01:25, Hyman Huang wrote:
> Introudce option to enable dirty-limit convergence algorithim
> during live migration.
>
> Signed-off-by: Hyman Huang <yong.huang@xxxxxxxxxx>
> ---
> docs/manpages/virsh.rst | 10 +++++++++-
> src/libvirt-domain.c | 8 ++++++++
> tools/virsh-domain.c | 10 ++++++++++
> 3 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst
> index 3e7a4c6c22..d1d20cb5ba 100644
> --- a/docs/manpages/virsh.rst
> +++ b/docs/manpages/virsh.rst
> @@ -3376,7 +3376,7 @@ migrate
> [--compressed] [--comp-methods method-list]
> [--comp-mt-level] [--comp-mt-threads] [--comp-mt-dthreads]
> [--comp-xbzrle-cache] [--comp-zlib-level] [--comp-zstd-level]
> - [--auto-converge] [auto-converge-initial]
> + [--dirty-limit] [--auto-converge] [auto-converge-initial]
> [auto-converge-increment] [--persistent-xml file] [--tls]
> [--postcopy-bandwidth bandwidth]
> [--parallel [--parallel-connections connections]]
> @@ -3432,6 +3432,14 @@ source or destination host and the ``migrate`` command will report an error
> leaving the domain active on both hosts. To recover from such situation repeat
> the original ``migrate`` command with an additional *--postcopy-resume* flag.
>
> +*--dirty-limit* forces convergence using dirty-limit algorithms during live
> +migration. For QEMU/KVM, this means migration will throttle vCPUs as needed to
> +keep their dirty page rate within the migration parameter ``vcpu-dirty-limit``
> +(1 megabits/s by default). This can improve the responsiveness of large guests
So how are users supposed to set this dirty limit value? I wonder
whether we should make --dirty-limit accept a value and then have the
QEMU driver call 'set-vcpu-dirty-limit' monitor command with desired value.
Except, the monitor command allows setting different value for each
vCPU. I'm not sure our APIs are flexible enough to express that. Jirka?
> +during live migration and result in more stable read performance. It requires
> +dirty-ring size configuration and conflicts with the traditional
> +``auto-converge`` algorithm.
> +
> *--auto-converge* forces convergence during live migration. The initial
> guest CPU throttling rate can be set with *auto-converge-initial*. If the
> initial throttling rate is not enough to ensure convergence, the rate is
> diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
> index 77a9682ecb..dde60ab05b 100644
> --- a/src/libvirt-domain.c
> +++ b/src/libvirt-domain.c
> @@ -4227,6 +4227,10 @@ virDomainMigrate3(virDomainPtr domain,
> /* Now checkout the destination */
> virCheckReadOnlyGoto(dconn->flags, error);
>
> + VIR_EXCLUSIVE_FLAGS_GOTO(VIR_MIGRATE_AUTO_CONVERGE,
> + VIR_MIGRATE_DIRTY_LIMIT,
> + error);
> +
> VIR_EXCLUSIVE_FLAGS_GOTO(VIR_MIGRATE_NON_SHARED_DISK,
> VIR_MIGRATE_NON_SHARED_INC,
> error);
> @@ -4652,6 +4656,10 @@ virDomainMigrateToURI3(virDomainPtr domain,
> virCheckDomainReturn(domain, -1);
> virCheckReadOnlyGoto(domain->conn->flags, error);
>
> + VIR_EXCLUSIVE_FLAGS_GOTO(VIR_MIGRATE_AUTO_CONVERGE,
> + VIR_MIGRATE_DIRTY_LIMIT,
> + error);
> +
> VIR_EXCLUSIVE_FLAGS_GOTO(VIR_MIGRATE_TUNNELLED,
> VIR_MIGRATE_PARALLEL,
> error);
> diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
> index 66f933dead..3f34230e6b 100644
> --- a/tools/virsh-domain.c
> +++ b/tools/virsh-domain.c
> @@ -10981,6 +10981,10 @@ static const vshCmdOptDef opts_migrate[] = {
> .type = VSH_OT_BOOL,
> .help = N_("compress repeated pages during live migration")
> },
> + {.name = "dirty-limit",
> + .type = VSH_OT_BOOL,
> + .help = N_("force convergence with dirty-limit algorithim during live migration")
> + },
> {.name = "auto-converge",
> .type = VSH_OT_BOOL,
> .help = N_("force convergence during live migration")
> @@ -11167,6 +11171,7 @@ doMigrate(void *opaque)
> { "change-protection", VIR_MIGRATE_CHANGE_PROTECTION },
> { "unsafe", VIR_MIGRATE_UNSAFE },
> { "compressed", VIR_MIGRATE_COMPRESSED },
> + { "dirty-limit", VIR_MIGRATE_DIRTY_LIMIT },
> { "auto-converge", VIR_MIGRATE_AUTO_CONVERGE },
> { "rdma-pin-all", VIR_MIGRATE_RDMA_PIN_ALL },
> { "offline", VIR_MIGRATE_OFFLINE },
> @@ -11193,6 +11198,11 @@ doMigrate(void *opaque)
> flags |= flagmap[i].migflag;
> }
>
> + if (flags & VIR_MIGRATE_DIRTY_LIMIT && flags & VIR_MIGRATE_AUTO_CONVERGE) {
> + vshError(ctl, "'--dirty-limit' conflicts with '--auto-converge'");
> + goto out;
> + }
> +
This doesn't belong here, but into the caller: cmdMigrate(). And it can
be simplified too:
VSH_EXCLUSIVE_OPTIONS("dirty-limit", "auto-converge");
> if (flags & VIR_MIGRATE_NON_SHARED_SYNCHRONOUS_WRITES &&
> !(flags & (VIR_MIGRATE_NON_SHARED_DISK | VIR_MIGRATE_NON_SHARED_DISK))) {
> vshError(ctl, "'--copy-storage-synchronous-writes' requires one of '--copy-storage-all', '--copy-storage-inc'");
Also looks spurious, but pre-existing.
Michal
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