| Message ID | 20200924195058.362984-3-danielhb413@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | pseries NUMA distance calculation | expand |
On Thu, Sep 24, 2020 at 04:50:54PM -0300, Daniel Henrique Barboza wrote: > The pSeries machine does not support asymmetrical NUMA > configurations. This doesn't make much of a different > since we're not using user input for pSeries NUMA setup, > but this will change in the next patches. > > To avoid breaking existing setups, gate this change by > checking for legacy NUMA support. > > Reviewed-by: Greg Kurz <groug@kaod.org> > Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> > --- > hw/ppc/spapr_numa.c | 34 ++++++++++++++++++++++++++++++++++ > 1 file changed, 34 insertions(+) > > diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c > index 64fe567f5d..fe395e80a3 100644 > --- a/hw/ppc/spapr_numa.c > +++ b/hw/ppc/spapr_numa.c > @@ -19,6 +19,24 @@ > /* Moved from hw/ppc/spapr_pci_nvlink2.c */ > #define SPAPR_GPU_NUMA_ID (cpu_to_be32(1)) > > +static bool spapr_numa_is_symmetrical(MachineState *ms) > +{ > + int src, dst; > + int nb_numa_nodes = ms->numa_state->num_nodes; > + NodeInfo *numa_info = ms->numa_state->nodes; > + > + for (src = 0; src < nb_numa_nodes; src++) { > + for (dst = src; dst < nb_numa_nodes; dst++) { > + if (numa_info[src].distance[dst] != > + numa_info[dst].distance[src]) { > + return false; > + } > + } > + } > + > + return true; > +} > + > void spapr_numa_associativity_init(SpaprMachineState *spapr, > MachineState *machine) > { > @@ -61,6 +79,22 @@ void spapr_numa_associativity_init(SpaprMachineState *spapr, > > spapr->numa_assoc_array[i][MAX_DISTANCE_REF_POINTS] = cpu_to_be32(i); > } > + > + /* > + * Legacy NUMA guests (pseries-5.1 and older, or guests with only > + * 1 NUMA node) will not benefit from anything we're going to do > + * after this point. > + */ > + if (spapr_machine_using_legacy_numa(spapr)) { > + return; > + } > + > + if (!spapr_numa_is_symmetrical(machine)) { > + error_report("Asymmetrical NUMA topologies aren't supported " > + "in the pSeries machine"); > + exit(EXIT_FAILURE); > + } > + > } > > void spapr_numa_write_associativity_dt(SpaprMachineState *spapr, void *fdt,
On Thu, Sep 24, 2020 at 04:50:54PM -0300, Daniel Henrique Barboza wrote: > The pSeries machine does not support asymmetrical NUMA > configurations. This doesn't make much of a different > since we're not using user input for pSeries NUMA setup, > but this will change in the next patches. > > To avoid breaking existing setups, gate this change by > checking for legacy NUMA support. > > Reviewed-by: Greg Kurz <groug@kaod.org> > Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> Having read the rest of the series, I realized there's another type of configuration that PAPR can't represent, so possibly we should add logic to catch that as well. That's what I'm going to call "non-transitive" configurations, e.g. Node 0 1 2 0 10 20 40 1 20 10 20 2 40 20 10 Basically the closeness of 0 to 1 and 1 to 2 forces them all to be in the same domain at every PAPR level, even though 0-2 is supposed to be more expensive. > --- > hw/ppc/spapr_numa.c | 34 ++++++++++++++++++++++++++++++++++ > 1 file changed, 34 insertions(+) > > diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c > index 64fe567f5d..fe395e80a3 100644 > --- a/hw/ppc/spapr_numa.c > +++ b/hw/ppc/spapr_numa.c > @@ -19,6 +19,24 @@ > /* Moved from hw/ppc/spapr_pci_nvlink2.c */ > #define SPAPR_GPU_NUMA_ID (cpu_to_be32(1)) > > +static bool spapr_numa_is_symmetrical(MachineState *ms) > +{ > + int src, dst; > + int nb_numa_nodes = ms->numa_state->num_nodes; > + NodeInfo *numa_info = ms->numa_state->nodes; > + > + for (src = 0; src < nb_numa_nodes; src++) { > + for (dst = src; dst < nb_numa_nodes; dst++) { > + if (numa_info[src].distance[dst] != > + numa_info[dst].distance[src]) { > + return false; > + } > + } > + } > + > + return true; > +} > + > void spapr_numa_associativity_init(SpaprMachineState *spapr, > MachineState *machine) > { > @@ -61,6 +79,22 @@ void spapr_numa_associativity_init(SpaprMachineState *spapr, > > spapr->numa_assoc_array[i][MAX_DISTANCE_REF_POINTS] = cpu_to_be32(i); > } > + > + /* > + * Legacy NUMA guests (pseries-5.1 and older, or guests with only > + * 1 NUMA node) will not benefit from anything we're going to do > + * after this point. > + */ > + if (spapr_machine_using_legacy_numa(spapr)) { > + return; > + } > + > + if (!spapr_numa_is_symmetrical(machine)) { > + error_report("Asymmetrical NUMA topologies aren't supported " > + "in the pSeries machine"); > + exit(EXIT_FAILURE); > + } > + > } > > void spapr_numa_write_associativity_dt(SpaprMachineState *spapr, void *fdt,
On 9/25/20 12:48 AM, David Gibson wrote: > On Thu, Sep 24, 2020 at 04:50:54PM -0300, Daniel Henrique Barboza wrote: >> The pSeries machine does not support asymmetrical NUMA >> configurations. This doesn't make much of a different >> since we're not using user input for pSeries NUMA setup, >> but this will change in the next patches. >> >> To avoid breaking existing setups, gate this change by >> checking for legacy NUMA support. >> >> Reviewed-by: Greg Kurz <groug@kaod.org> >> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> > > Having read the rest of the series, I realized there's another type of > configuration that PAPR can't represent, so possibly we should add > logic to catch that as well. That's what I'm going to call > "non-transitive" configurations, e.g. > > Node 0 1 2 > 0 10 20 40 > 1 20 10 20 > 2 40 20 10 > > Basically the closeness of 0 to 1 and 1 to 2 forces them all to be in > the same domain at every PAPR level, even though 0-2 is supposed to be > more expensive. Yes, this is correct. I'm not sure how to proceed in this case though. Should we error out? DHB > >> --- >> hw/ppc/spapr_numa.c | 34 ++++++++++++++++++++++++++++++++++ >> 1 file changed, 34 insertions(+) >> >> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c >> index 64fe567f5d..fe395e80a3 100644 >> --- a/hw/ppc/spapr_numa.c >> +++ b/hw/ppc/spapr_numa.c >> @@ -19,6 +19,24 @@ >> /* Moved from hw/ppc/spapr_pci_nvlink2.c */ >> #define SPAPR_GPU_NUMA_ID (cpu_to_be32(1)) >> >> +static bool spapr_numa_is_symmetrical(MachineState *ms) >> +{ >> + int src, dst; >> + int nb_numa_nodes = ms->numa_state->num_nodes; >> + NodeInfo *numa_info = ms->numa_state->nodes; >> + >> + for (src = 0; src < nb_numa_nodes; src++) { >> + for (dst = src; dst < nb_numa_nodes; dst++) { >> + if (numa_info[src].distance[dst] != >> + numa_info[dst].distance[src]) { >> + return false; >> + } >> + } >> + } >> + >> + return true; >> +} >> + >> void spapr_numa_associativity_init(SpaprMachineState *spapr, >> MachineState *machine) >> { >> @@ -61,6 +79,22 @@ void spapr_numa_associativity_init(SpaprMachineState *spapr, >> >> spapr->numa_assoc_array[i][MAX_DISTANCE_REF_POINTS] = cpu_to_be32(i); >> } >> + >> + /* >> + * Legacy NUMA guests (pseries-5.1 and older, or guests with only >> + * 1 NUMA node) will not benefit from anything we're going to do >> + * after this point. >> + */ >> + if (spapr_machine_using_legacy_numa(spapr)) { >> + return; >> + } >> + >> + if (!spapr_numa_is_symmetrical(machine)) { >> + error_report("Asymmetrical NUMA topologies aren't supported " >> + "in the pSeries machine"); >> + exit(EXIT_FAILURE); >> + } >> + >> } >> >> void spapr_numa_write_associativity_dt(SpaprMachineState *spapr, void *fdt, >
On Fri, Sep 25, 2020 at 09:41:02AM -0300, Daniel Henrique Barboza wrote: > > > On 9/25/20 12:48 AM, David Gibson wrote: > > On Thu, Sep 24, 2020 at 04:50:54PM -0300, Daniel Henrique Barboza wrote: > > > The pSeries machine does not support asymmetrical NUMA > > > configurations. This doesn't make much of a different > > > since we're not using user input for pSeries NUMA setup, > > > but this will change in the next patches. > > > > > > To avoid breaking existing setups, gate this change by > > > checking for legacy NUMA support. > > > > > > Reviewed-by: Greg Kurz <groug@kaod.org> > > > Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> > > > > Having read the rest of the series, I realized there's another type of > > configuration that PAPR can't represent, so possibly we should add > > logic to catch that as well. That's what I'm going to call > > "non-transitive" configurations, e.g. > > > > Node 0 1 2 > > 0 10 20 40 > > 1 20 10 20 > > 2 40 20 10 > > > > Basically the closeness of 0 to 1 and 1 to 2 forces them all to be in > > the same domain at every PAPR level, even though 0-2 is supposed to be > > more expensive. > > Yes, this is correct. I'm not sure how to proceed in this case > though. Should we error out? Given that we're already erroring on asymmetric configurations, I think it makes sense to error for these as well.
On 9/26/20 4:49 AM, David Gibson wrote: > On Fri, Sep 25, 2020 at 09:41:02AM -0300, Daniel Henrique Barboza wrote: >> >> >> On 9/25/20 12:48 AM, David Gibson wrote: >>> On Thu, Sep 24, 2020 at 04:50:54PM -0300, Daniel Henrique Barboza wrote: >>>> The pSeries machine does not support asymmetrical NUMA >>>> configurations. This doesn't make much of a different >>>> since we're not using user input for pSeries NUMA setup, >>>> but this will change in the next patches. >>>> >>>> To avoid breaking existing setups, gate this change by >>>> checking for legacy NUMA support. >>>> >>>> Reviewed-by: Greg Kurz <groug@kaod.org> >>>> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> >>> >>> Having read the rest of the series, I realized there's another type of >>> configuration that PAPR can't represent, so possibly we should add >>> logic to catch that as well. That's what I'm going to call >>> "non-transitive" configurations, e.g. >>> >>> Node 0 1 2 >>> 0 10 20 40 >>> 1 20 10 20 >>> 2 40 20 10 >>> >>> Basically the closeness of 0 to 1 and 1 to 2 forces them all to be in >>> the same domain at every PAPR level, even though 0-2 is supposed to be >>> more expensive. >> >> Yes, this is correct. I'm not sure how to proceed in this case >> though. Should we error out? > > Given that we're already erroring on asymmetric configurations, I > think it makes sense to error for these as well. Thing is that asymmetrical configurations is an easy concept to enforce to the user - distance from A to B can't be different from B to A. In the example you gave above, with 3 NUMA nodes, is easy to spot where the non-transitivity rule would hit. I'm afraid that if we add 2-3 more NUMA nodes in the mix this will stop being straightforward, with more and more combinations hitting the 'non-transitivity' rule, and erroring out will end up being frustrating to the user. I'd say that we should report this in the documentation as one more limitation of the implementation (and PAPR). I wouldn't oppose with throwing a warning message either, letting the user know that the approximation will be less precise than it already would be in this case. Thanks, DHB >
On Sun, Sep 27, 2020 at 08:41:30AM -0300, Daniel Henrique Barboza wrote: > > > On 9/26/20 4:49 AM, David Gibson wrote: > > On Fri, Sep 25, 2020 at 09:41:02AM -0300, Daniel Henrique Barboza wrote: > > > > > > > > > On 9/25/20 12:48 AM, David Gibson wrote: > > > > On Thu, Sep 24, 2020 at 04:50:54PM -0300, Daniel Henrique Barboza wrote: > > > > > The pSeries machine does not support asymmetrical NUMA > > > > > configurations. This doesn't make much of a different > > > > > since we're not using user input for pSeries NUMA setup, > > > > > but this will change in the next patches. > > > > > > > > > > To avoid breaking existing setups, gate this change by > > > > > checking for legacy NUMA support. > > > > > > > > > > Reviewed-by: Greg Kurz <groug@kaod.org> > > > > > Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> > > > > > > > > Having read the rest of the series, I realized there's another type of > > > > configuration that PAPR can't represent, so possibly we should add > > > > logic to catch that as well. That's what I'm going to call > > > > "non-transitive" configurations, e.g. > > > > > > > > Node 0 1 2 > > > > 0 10 20 40 > > > > 1 20 10 20 > > > > 2 40 20 10 > > > > > > > > Basically the closeness of 0 to 1 and 1 to 2 forces them all to be in > > > > the same domain at every PAPR level, even though 0-2 is supposed to be > > > > more expensive. > > > > > > Yes, this is correct. I'm not sure how to proceed in this case > > > though. Should we error out? > > > > Given that we're already erroring on asymmetric configurations, I > > think it makes sense to error for these as well. > > Thing is that asymmetrical configurations is an easy concept to enforce > to the user - distance from A to B can't be different from B to A. > > In the example you gave above, with 3 NUMA nodes, is easy to spot where > the non-transitivity rule would hit. I'm afraid that if we add 2-3 more > NUMA nodes in the mix this will stop being straightforward, with more and > more combinations hitting the 'non-transitivity' rule, and erroring out > will end up being frustrating to the user. > > I'd say that we should report this in the documentation as one more > limitation of the implementation (and PAPR). I wouldn't oppose with > throwing a warning message either, letting the user know that the > approximation will be less precise than it already would be in this > case. Hmm... yes, I see your point. Ok, let's go with your suggestion.
diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c index 64fe567f5d..fe395e80a3 100644 --- a/hw/ppc/spapr_numa.c +++ b/hw/ppc/spapr_numa.c @@ -19,6 +19,24 @@ /* Moved from hw/ppc/spapr_pci_nvlink2.c */ #define SPAPR_GPU_NUMA_ID (cpu_to_be32(1)) +static bool spapr_numa_is_symmetrical(MachineState *ms) +{ + int src, dst; + int nb_numa_nodes = ms->numa_state->num_nodes; + NodeInfo *numa_info = ms->numa_state->nodes; + + for (src = 0; src < nb_numa_nodes; src++) { + for (dst = src; dst < nb_numa_nodes; dst++) { + if (numa_info[src].distance[dst] != + numa_info[dst].distance[src]) { + return false; + } + } + } + + return true; +} + void spapr_numa_associativity_init(SpaprMachineState *spapr, MachineState *machine) { @@ -61,6 +79,22 @@ void spapr_numa_associativity_init(SpaprMachineState *spapr, spapr->numa_assoc_array[i][MAX_DISTANCE_REF_POINTS] = cpu_to_be32(i); } + + /* + * Legacy NUMA guests (pseries-5.1 and older, or guests with only + * 1 NUMA node) will not benefit from anything we're going to do + * after this point. + */ + if (spapr_machine_using_legacy_numa(spapr)) { + return; + } + + if (!spapr_numa_is_symmetrical(machine)) { + error_report("Asymmetrical NUMA topologies aren't supported " + "in the pSeries machine"); + exit(EXIT_FAILURE); + } + } void spapr_numa_write_associativity_dt(SpaprMachineState *spapr, void *fdt,