| Message ID | 1433763511-5270-8-git-send-email-khandual@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Mon, 2015-06-08 at 17:08 +0530, Anshuman Khandual wrote: > The kernel now supports SW based branch filters for book3s systems with > some specific requirements while dealing with HW supported branch filters > in order to achieve overall OR semantics prevailing in perf branch stack > sampling framework. This patch adapts the BHRB branch filter configuration > to meet those protocols. POWER8 PMU can only handle one HW based branch > filter request at any point of time. For all other combinations PMU will > pass it on to the SW. > > Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com> > --- > arch/powerpc/perf/power8-pmu.c | 51 ++++++++++++++++++++++++++++++++++++------ > 1 file changed, 44 insertions(+), 7 deletions(-) > > diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c > index 5e17cb5..8fccf6c 100644 > --- a/arch/powerpc/perf/power8-pmu.c > +++ b/arch/powerpc/perf/power8-pmu.c > @@ -656,6 +656,16 @@ static int power8_generic_events[] = { > This is, I think, the third time you've modified this function in this patch series. I appreciate the fact that you're trying to keep logical changes separate, but it seems to me like this change might be able to be combined with patch 4, and given a single commit message that clearly explains the complete scope of the changes. > static u64 power8_bhrb_filter_map(u64 branch_sample_type, u64 *bhrb_filter) > { > + u64 x, pmu_bhrb_filter; > + > + pmu_bhrb_filter = 0; > + *bhrb_filter = 0; > + > + if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY) { > + *bhrb_filter = PERF_SAMPLE_BRANCH_ANY; > + return pmu_bhrb_filter; > + } > + > /* BHRB and regular PMU events share the same privilege state > * filter configuration. BHRB is always recorded along with a > * regular PMU event. As the privilege state filter is handled > @@ -666,15 +676,42 @@ static u64 power8_bhrb_filter_map(u64 branch_sample_type, u64 *bhrb_filter) > /* Ignore user, kernel, hv bits */ > branch_sample_type &= ~PERF_SAMPLE_BRANCH_PLM_ALL; > > - /* No branch filter requested */ > - if (branch_sample_type == PERF_SAMPLE_BRANCH_ANY) > - return 0; > + /* > + * POWER8 does not support ORing of PMU HW branch filters. Hence > + * if multiple branch filters are requested which may include filters > + * supported in PMU, still go ahead and clear the PMU based HW branch > + * filter component as in this case all the filters will be processed > + * in SW. > + */ > > - if (branch_sample_type == PERF_SAMPLE_BRANCH_ANY_CALL) > - return POWER8_MMCRA_IFM1; > + for_each_branch_sample_type(x) { > + /* Ignore privilege branch filters */ > + if ((x == PERF_SAMPLE_BRANCH_USER) > + || (x == PERF_SAMPLE_BRANCH_KERNEL) > + || (x == PERF_SAMPLE_BRANCH_HV)) > + continue; > + > + if (!(branch_sample_type & x)) > + continue; > + > + /* Supported individual PMU branch filters */ > + if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY_CALL) { > + branch_sample_type &= ~PERF_SAMPLE_BRANCH_ANY_CALL; > + if (branch_sample_type) { > + /* Multiple filters will be processed in SW */ > + pmu_bhrb_filter = 0; > + *bhrb_filter = 0; > + return pmu_bhrb_filter; > + } else { > + /* Individual filter will be processed in HW */ > + pmu_bhrb_filter |= POWER8_MMCRA_IFM1; > + *bhrb_filter |= PERF_SAMPLE_BRANCH_ANY_CALL; > + return pmu_bhrb_filter; > + } > + } > + } > > - /* Every thing else is unsupported */ > - return -1; > + return pmu_bhrb_filter; > } Regards, Daniel
On 06/10/2015 11:19 AM, Daniel Axtens wrote: > On Mon, 2015-06-08 at 17:08 +0530, Anshuman Khandual wrote: >> > The kernel now supports SW based branch filters for book3s systems with >> > some specific requirements while dealing with HW supported branch filters >> > in order to achieve overall OR semantics prevailing in perf branch stack >> > sampling framework. This patch adapts the BHRB branch filter configuration >> > to meet those protocols. POWER8 PMU can only handle one HW based branch >> > filter request at any point of time. For all other combinations PMU will >> > pass it on to the SW. >> > >> > Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com> >> > --- >> > arch/powerpc/perf/power8-pmu.c | 51 ++++++++++++++++++++++++++++++++++++------ >> > 1 file changed, 44 insertions(+), 7 deletions(-) >> > >> > diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c >> > index 5e17cb5..8fccf6c 100644 >> > --- a/arch/powerpc/perf/power8-pmu.c >> > +++ b/arch/powerpc/perf/power8-pmu.c >> > @@ -656,6 +656,16 @@ static int power8_generic_events[] = { >> > > This is, I think, the third time you've modified this function in this > patch series. I appreciate the fact that you're trying to keep logical > changes separate, but it seems to me like this change might be able to > be combined with patch 4, and given a single commit message that clearly > explains the complete scope of the changes. Here I have to disagree with you. The changes in this patch like PMU should not handle multiple filter requests as it does not support the OR semantic required in the protocol, the fact that we need to pass on the entire branch filtering responsibility to the SW comes into picture after we have enabled the SW branch filtering support in the previous patch. So these changes have to follow that up logically and sequentially in that order.
On Wed, 2015-06-10 at 17:40 +0530, Anshuman Khandual wrote: > On 06/10/2015 11:19 AM, Daniel Axtens wrote: > > On Mon, 2015-06-08 at 17:08 +0530, Anshuman Khandual wrote: > >> > The kernel now supports SW based branch filters for book3s systems with > >> > some specific requirements while dealing with HW supported branch filters > >> > in order to achieve overall OR semantics prevailing in perf branch stack > >> > sampling framework. This patch adapts the BHRB branch filter configuration > >> > to meet those protocols. POWER8 PMU can only handle one HW based branch > >> > filter request at any point of time. For all other combinations PMU will > >> > pass it on to the SW. > >> > > >> > Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com> > >> > --- > >> > arch/powerpc/perf/power8-pmu.c | 51 ++++++++++++++++++++++++++++++++++++------ > >> > 1 file changed, 44 insertions(+), 7 deletions(-) > >> > > >> > diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c > >> > index 5e17cb5..8fccf6c 100644 > >> > --- a/arch/powerpc/perf/power8-pmu.c > >> > +++ b/arch/powerpc/perf/power8-pmu.c > >> > @@ -656,6 +656,16 @@ static int power8_generic_events[] = { > >> > > > This is, I think, the third time you've modified this function in this > > patch series. I appreciate the fact that you're trying to keep logical > > changes separate, but it seems to me like this change might be able to > > be combined with patch 4, and given a single commit message that clearly > > explains the complete scope of the changes. > > Here I have to disagree with you. The changes in this patch like PMU > should not handle multiple filter requests as it does not support the > OR semantic required in the protocol, the fact that we need to pass > on the entire branch filtering responsibility to the SW comes into > picture after we have enabled the SW branch filtering support in the > previous patch. So these changes have to follow that up logically and > sequentially in that order. > OK. I don't think I understand the patch set quite well enough to follow your logic, but when you send out the next version I'll try to take a closer look at how the series fits together as a whole.
diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c index 5e17cb5..8fccf6c 100644 --- a/arch/powerpc/perf/power8-pmu.c +++ b/arch/powerpc/perf/power8-pmu.c @@ -656,6 +656,16 @@ static int power8_generic_events[] = { static u64 power8_bhrb_filter_map(u64 branch_sample_type, u64 *bhrb_filter) { + u64 x, pmu_bhrb_filter; + + pmu_bhrb_filter = 0; + *bhrb_filter = 0; + + if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY) { + *bhrb_filter = PERF_SAMPLE_BRANCH_ANY; + return pmu_bhrb_filter; + } + /* BHRB and regular PMU events share the same privilege state * filter configuration. BHRB is always recorded along with a * regular PMU event. As the privilege state filter is handled @@ -666,15 +676,42 @@ static u64 power8_bhrb_filter_map(u64 branch_sample_type, u64 *bhrb_filter) /* Ignore user, kernel, hv bits */ branch_sample_type &= ~PERF_SAMPLE_BRANCH_PLM_ALL; - /* No branch filter requested */ - if (branch_sample_type == PERF_SAMPLE_BRANCH_ANY) - return 0; + /* + * POWER8 does not support ORing of PMU HW branch filters. Hence + * if multiple branch filters are requested which may include filters + * supported in PMU, still go ahead and clear the PMU based HW branch + * filter component as in this case all the filters will be processed + * in SW. + */ - if (branch_sample_type == PERF_SAMPLE_BRANCH_ANY_CALL) - return POWER8_MMCRA_IFM1; + for_each_branch_sample_type(x) { + /* Ignore privilege branch filters */ + if ((x == PERF_SAMPLE_BRANCH_USER) + || (x == PERF_SAMPLE_BRANCH_KERNEL) + || (x == PERF_SAMPLE_BRANCH_HV)) + continue; + + if (!(branch_sample_type & x)) + continue; + + /* Supported individual PMU branch filters */ + if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY_CALL) { + branch_sample_type &= ~PERF_SAMPLE_BRANCH_ANY_CALL; + if (branch_sample_type) { + /* Multiple filters will be processed in SW */ + pmu_bhrb_filter = 0; + *bhrb_filter = 0; + return pmu_bhrb_filter; + } else { + /* Individual filter will be processed in HW */ + pmu_bhrb_filter |= POWER8_MMCRA_IFM1; + *bhrb_filter |= PERF_SAMPLE_BRANCH_ANY_CALL; + return pmu_bhrb_filter; + } + } + } - /* Every thing else is unsupported */ - return -1; + return pmu_bhrb_filter; } static void power8_config_bhrb(u64 pmu_bhrb_filter)
The kernel now supports SW based branch filters for book3s systems with some specific requirements while dealing with HW supported branch filters in order to achieve overall OR semantics prevailing in perf branch stack sampling framework. This patch adapts the BHRB branch filter configuration to meet those protocols. POWER8 PMU can only handle one HW based branch filter request at any point of time. For all other combinations PMU will pass it on to the SW. Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com> --- arch/powerpc/perf/power8-pmu.c | 51 ++++++++++++++++++++++++++++++++++++------ 1 file changed, 44 insertions(+), 7 deletions(-)