| Message ID | 1506160104-5890-16-git-send-email-yi.y.sun@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, Sep 23, 2017 at 09:48:24AM +0000, Yi Sun wrote: > This patch adds MBA description in related documents. > > Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com> > Acked-by: Wei Liu <wei.liu2@citrix.com> There's still a 'closed-loop' mention that I think I've already pointed out in the last review, but anyway: Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> > --- > CC: Wei Liu <wei.liu2@citrix.com> > CC: Ian Jackson <ian.jackson@eu.citrix.com> > CC: Roger Pau Monné <roger.pau@citrix.com> > CC: Chao Peng <chao.p.peng@linux.intel.com> > > v4: > - modify description of MBA in 'xl.pod.1.in' to be same as feature doc. > (suggested by Roger Pau Monné) > - fix words issue. > (suggested by Roger Pau Monné) > v2: > - state the value type shown by 'psr-mba-show'. For linear mode, > it shows decimal value. For non-linear mode, it shows hexadecimal > value. > (suggested by Chao Peng) > --- > docs/man/xl.pod.1.in | 33 +++++++++++++++++++++++++ > docs/misc/xl-psr.markdown | 63 +++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 96 insertions(+) > > diff --git a/docs/man/xl.pod.1.in b/docs/man/xl.pod.1.in > index 3d5f2f7..64d87ba 100644 > --- a/docs/man/xl.pod.1.in > +++ b/docs/man/xl.pod.1.in > @@ -1803,6 +1803,39 @@ processed. > > =back > > +=head2 Memory Bandwidth Allocation > + > +Intel Skylake and later server platforms offer capabilities to configure and > +make use of the Memory Bandwidth Allocation (MBA) mechanisms, which provides > +OS/VMMs the ability to slow misbehaving apps/VMs by using a credit-based > +throttling mechanism. In the Xen implementation, MBA is used to control memory > +bandwidth on VM basis. To enforce bandwidth on a specific domain, just set > +throttling value (THRTL) for the domain. > + > +=over 4 > + > +=item B<psr-mba-set> [I<OPTIONS>] I<domain-id> I<thrtl> > + > +Set throttling value (THRTL) for a domain. For how to specify I<thrtl> > +please refer to L<http://xenbits.xen.org/docs/unstable/misc/xl-psr.html>. > + > +B<OPTIONS> > + > +=over 4 > + > +=item B<-s SOCKET>, B<--socket=SOCKET> > + > +Specify the socket to process, otherwise all sockets are processed. > + > +=back > + > +=item B<psr-mba-show> [I<domain-id>] > + > +Show MBA settings for a certain domain or all domains. For linear mode, it > +shows the decimal value. For non-linear mode, it shows hexadecimal value. > + > +=back > + > =head1 IGNORED FOR COMPATIBILITY WITH XM > > xl is mostly command-line compatible with the old xm utility used with > diff --git a/docs/misc/xl-psr.markdown b/docs/misc/xl-psr.markdown > index 04dd957..08c06dc 100644 > --- a/docs/misc/xl-psr.markdown > +++ b/docs/misc/xl-psr.markdown > @@ -186,6 +186,69 @@ Setting data CBM for a domain: > Setting the same code and data CBM for a domain: > `xl psr-cat-set <domid> <cbm>` > > +## Memory Bandwidth Allocation (MBA) > + > +Memory Bandwidth Allocation (MBA) is a new feature available on Intel > +Skylake and later server platforms that allows an OS or Hypervisor/VMM to > +slow misbehaving apps/VMs or create advanced closed-loop control system via > +exposing control over a credit-based throttling mechanism. To enforce bandwidth > +on a specific domain, just set throttling value (THRTL) into Class of Service > +(COS). MBA provides two THRTL mode. One is linear mode and the other is > +non-linear mode. > + > +In the linear mode the input precision is defined as 100-(THRTL_MAX). Values > +not an even multiple of the precision (e.g., 12%) will be rounded down (e.g., > +to 10% delay by the hardware). > + > +If linear values are not supported then input delay values are powers-of-two > +from zero to the THRTL_MAX value from CPUID. In this case any values not a power > +of two will be rounded down the next nearest power of two. > + > +For example, assuming a system with 2 domains: > + > + * A THRTL of 0x0 for every domain means each domain can access the whole cache > + without any delay. This is the default. > + > + * Linear mode: Giving one domain a THRTL of 0xC and the other domain's 0 means > + that the first domain gets 10% delay to access the cache and the other one > + without any delay. > + > + * Non-linear mode: Giving one domain a THRTL of 0xC and the other domain's 0 > + means that the first domain gets 8% delay to access the cache and the other > + one without any delay. > + > +For more detailed information please refer to Intel SDM chapter > +"Introduction to Memory Bandwidth Allocation". > + > +In Xen's implementation, THRTL can be configured with libxl/xl interfaces but > +COS is maintained in hypervisor only. The cache partition granularity is per > +domain, each domain has COS=0 assigned by default, the corresponding THRTL is > +0, which means all the cache resource can be accessed without delay. > + > +### xl interfaces > + > +System MBA information such as maximum COS and maximum THRTL can be obtained by: > + > +`xl psr-hwinfo --mba` > + > +The simplest way to change a domain's THRTL from its default is running: > + > +`xl psr-mba-set [OPTIONS] <domid> <thrtl>` > + > +In a multi-socket system, the same thrtl will be set on each socket by default. > +Per socket thrtl can be specified with the `--socket SOCKET` option. > + > +Setting the THRTL may not be successful if insufficient COS is available. In ^ not enough COS are available. > +such case unused COS(es) may be freed by setting THRTL of all related domains to > +its default value(0). > + > +Per domain THRTL settings can be shown by: > + > +`xl psr-mba-show [OPTIONS] <domid>` > + > +For linear mode, it shows the decimal value. For non-linear mode, it shows > +hexadecimal value. > + > ## Reference > > [1] Intel SDM > -- > 1.9.1 >
diff --git a/docs/man/xl.pod.1.in b/docs/man/xl.pod.1.in index 3d5f2f7..64d87ba 100644 --- a/docs/man/xl.pod.1.in +++ b/docs/man/xl.pod.1.in @@ -1803,6 +1803,39 @@ processed. =back +=head2 Memory Bandwidth Allocation + +Intel Skylake and later server platforms offer capabilities to configure and +make use of the Memory Bandwidth Allocation (MBA) mechanisms, which provides +OS/VMMs the ability to slow misbehaving apps/VMs by using a credit-based +throttling mechanism. In the Xen implementation, MBA is used to control memory +bandwidth on VM basis. To enforce bandwidth on a specific domain, just set +throttling value (THRTL) for the domain. + +=over 4 + +=item B<psr-mba-set> [I<OPTIONS>] I<domain-id> I<thrtl> + +Set throttling value (THRTL) for a domain. For how to specify I<thrtl> +please refer to L<http://xenbits.xen.org/docs/unstable/misc/xl-psr.html>. + +B<OPTIONS> + +=over 4 + +=item B<-s SOCKET>, B<--socket=SOCKET> + +Specify the socket to process, otherwise all sockets are processed. + +=back + +=item B<psr-mba-show> [I<domain-id>] + +Show MBA settings for a certain domain or all domains. For linear mode, it +shows the decimal value. For non-linear mode, it shows hexadecimal value. + +=back + =head1 IGNORED FOR COMPATIBILITY WITH XM xl is mostly command-line compatible with the old xm utility used with diff --git a/docs/misc/xl-psr.markdown b/docs/misc/xl-psr.markdown index 04dd957..08c06dc 100644 --- a/docs/misc/xl-psr.markdown +++ b/docs/misc/xl-psr.markdown @@ -186,6 +186,69 @@ Setting data CBM for a domain: Setting the same code and data CBM for a domain: `xl psr-cat-set <domid> <cbm>` +## Memory Bandwidth Allocation (MBA) + +Memory Bandwidth Allocation (MBA) is a new feature available on Intel +Skylake and later server platforms that allows an OS or Hypervisor/VMM to +slow misbehaving apps/VMs or create advanced closed-loop control system via +exposing control over a credit-based throttling mechanism. To enforce bandwidth +on a specific domain, just set throttling value (THRTL) into Class of Service +(COS). MBA provides two THRTL mode. One is linear mode and the other is +non-linear mode. + +In the linear mode the input precision is defined as 100-(THRTL_MAX). Values +not an even multiple of the precision (e.g., 12%) will be rounded down (e.g., +to 10% delay by the hardware). + +If linear values are not supported then input delay values are powers-of-two +from zero to the THRTL_MAX value from CPUID. In this case any values not a power +of two will be rounded down the next nearest power of two. + +For example, assuming a system with 2 domains: + + * A THRTL of 0x0 for every domain means each domain can access the whole cache + without any delay. This is the default. + + * Linear mode: Giving one domain a THRTL of 0xC and the other domain's 0 means + that the first domain gets 10% delay to access the cache and the other one + without any delay. + + * Non-linear mode: Giving one domain a THRTL of 0xC and the other domain's 0 + means that the first domain gets 8% delay to access the cache and the other + one without any delay. + +For more detailed information please refer to Intel SDM chapter +"Introduction to Memory Bandwidth Allocation". + +In Xen's implementation, THRTL can be configured with libxl/xl interfaces but +COS is maintained in hypervisor only. The cache partition granularity is per +domain, each domain has COS=0 assigned by default, the corresponding THRTL is +0, which means all the cache resource can be accessed without delay. + +### xl interfaces + +System MBA information such as maximum COS and maximum THRTL can be obtained by: + +`xl psr-hwinfo --mba` + +The simplest way to change a domain's THRTL from its default is running: + +`xl psr-mba-set [OPTIONS] <domid> <thrtl>` + +In a multi-socket system, the same thrtl will be set on each socket by default. +Per socket thrtl can be specified with the `--socket SOCKET` option. + +Setting the THRTL may not be successful if insufficient COS is available. In +such case unused COS(es) may be freed by setting THRTL of all related domains to +its default value(0). + +Per domain THRTL settings can be shown by: + +`xl psr-mba-show [OPTIONS] <domid>` + +For linear mode, it shows the decimal value. For non-linear mode, it shows +hexadecimal value. + ## Reference [1] Intel SDM