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Message-ID: <87tw2kj2bm.fsf@concordia.ellerman.id.au>
Date: Mon, 10 Jul 2017 15:19:57 +1000
From: Michael Ellerman <mpe@...erman.id.au>
To: Peter Zijlstra <peterz@...radead.org>,
Jin Yao <yao.jin@...ux.intel.com>
Cc: ak@...ux.intel.com, maddy@...ux.vnet.ibm.com,
alexander.shishkin@...ux.intel.com, kan.liang@...el.com,
linuxppc-dev@...ts.ozlabs.org, Linux-kernel@...r.kernel.org,
acme@...nel.org, mingo@...hat.com, jolsa@...nel.org,
yao.jin@...el.com
Subject: Re: [PATCH v6 1/7] perf/core: Define the common branch type classification
Peter Zijlstra <peterz@...radead.org> writes:
> PPC folks, maddy, does this work for you guys?
It think it works for us, but I have some comments, I'll reply to the original.
cheers
> On Thu, Apr 20, 2017 at 08:07:49PM +0800, Jin Yao wrote:
>> It is often useful to know the branch types while analyzing branch
>> data. For example, a call is very different from a conditional branch.
>>
>> Currently we have to look it up in binary while the binary may later
>> not be available and even the binary is available but user has to take
>> some time. It is very useful for user to check it directly in perf
>> report.
>>
>> Perf already has support for disassembling the branch instruction
>> to get the x86 branch type.
>>
>> To keep consistent on kernel and userspace and make the classification
>> more common, the patch adds the common branch type classification
>> in perf_event.h.
>>
>> PERF_BR_NONE : unknown
>> PERF_BR_JCC : conditional jump
>> PERF_BR_JMP : jump
>> PERF_BR_IND_JMP : indirect jump
>> PERF_BR_CALL : call
>> PERF_BR_IND_CALL : indirect call
>> PERF_BR_RET : return
>> PERF_BR_SYSCALL : syscall
>> PERF_BR_SYSRET : syscall return
>> PERF_BR_IRQ : hw interrupt/trap/fault
>> PERF_BR_INT : sw interrupt
>> PERF_BR_IRET : return from interrupt
>> PERF_BR_FAR_BRANCH: not generic far branch type
>>
>> The patch also adds a new field type (4 bits) in perf_branch_entry
>> to record the branch type.
>>
>> Since the disassembling of branch instruction needs some overhead,
>> a new PERF_SAMPLE_BRANCH_TYPE_SAVE is introduced to indicate if it
>> needs to disassemble the branch instruction and record the branch
>> type.
>>
>> Change log
>> ----------
>>
>> v6: Not changed.
>>
>> v5: Not changed. The v5 patch series just change the userspace.
>>
>> v4: Comparing to previous version, the major changes are:
>>
>> 1. Remove the PERF_BR_JCC_FWD/PERF_BR_JCC_BWD, they will be
>> computed later in userspace.
>>
>> 2. Remove the "cross" field in perf_branch_entry. The cross page
>> computing will be done later in userspace.
>>
>> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
>> ---
>> include/uapi/linux/perf_event.h | 29 ++++++++++++++++++++++++++++-
>> tools/include/uapi/linux/perf_event.h | 29 ++++++++++++++++++++++++++++-
>> 2 files changed, 56 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
>> index d09a9cd..69af012 100644
>> --- a/include/uapi/linux/perf_event.h
>> +++ b/include/uapi/linux/perf_event.h
>> @@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
>> PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT = 14, /* no flags */
>> PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT = 15, /* no cycles */
>>
>> + PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT = 16, /* save branch type */
>> +
>> PERF_SAMPLE_BRANCH_MAX_SHIFT /* non-ABI */
>> };
>>
>> @@ -198,9 +200,32 @@ enum perf_branch_sample_type {
>> PERF_SAMPLE_BRANCH_NO_FLAGS = 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
>> PERF_SAMPLE_BRANCH_NO_CYCLES = 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
>>
>> + PERF_SAMPLE_BRANCH_TYPE_SAVE =
>> + 1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
>> +
>> PERF_SAMPLE_BRANCH_MAX = 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
>> };
>>
>> +/*
>> + * Common flow change classification
>> + */
>> +enum {
>> + PERF_BR_NONE = 0, /* unknown */
>> + PERF_BR_JCC = 1, /* conditional jump */
>> + PERF_BR_JMP = 2, /* jump */
>> + PERF_BR_IND_JMP = 3, /* indirect jump */
>> + PERF_BR_CALL = 4, /* call */
>> + PERF_BR_IND_CALL = 5, /* indirect call */
>> + PERF_BR_RET = 6, /* return */
>> + PERF_BR_SYSCALL = 7, /* syscall */
>> + PERF_BR_SYSRET = 8, /* syscall return */
>> + PERF_BR_IRQ = 9, /* hw interrupt/trap/fault */
>> + PERF_BR_INT = 10, /* sw interrupt */
>> + PERF_BR_IRET = 11, /* return from interrupt */
>> + PERF_BR_FAR_BRANCH = 12, /* not generic far branch type */
>> + PERF_BR_MAX,
>> +};
>> +
>> #define PERF_SAMPLE_BRANCH_PLM_ALL \
>> (PERF_SAMPLE_BRANCH_USER|\
>> PERF_SAMPLE_BRANCH_KERNEL|\
>> @@ -999,6 +1024,7 @@ union perf_mem_data_src {
>> * in_tx: running in a hardware transaction
>> * abort: aborting a hardware transaction
>> * cycles: cycles from last branch (or 0 if not supported)
>> + * type: branch type
>> */
>> struct perf_branch_entry {
>> __u64 from;
>> @@ -1008,7 +1034,8 @@ struct perf_branch_entry {
>> in_tx:1, /* in transaction */
>> abort:1, /* transaction abort */
>> cycles:16, /* cycle count to last branch */
>> - reserved:44;
>> + type:4, /* branch type */
>> + reserved:40;
>> };
>>
>> #endif /* _UAPI_LINUX_PERF_EVENT_H */
>> diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
>> index d09a9cd..69af012 100644
>> --- a/tools/include/uapi/linux/perf_event.h
>> +++ b/tools/include/uapi/linux/perf_event.h
>> @@ -174,6 +174,8 @@ enum perf_branch_sample_type_shift {
>> PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT = 14, /* no flags */
>> PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT = 15, /* no cycles */
>>
>> + PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT = 16, /* save branch type */
>> +
>> PERF_SAMPLE_BRANCH_MAX_SHIFT /* non-ABI */
>> };
>>
>> @@ -198,9 +200,32 @@ enum perf_branch_sample_type {
>> PERF_SAMPLE_BRANCH_NO_FLAGS = 1U << PERF_SAMPLE_BRANCH_NO_FLAGS_SHIFT,
>> PERF_SAMPLE_BRANCH_NO_CYCLES = 1U << PERF_SAMPLE_BRANCH_NO_CYCLES_SHIFT,
>>
>> + PERF_SAMPLE_BRANCH_TYPE_SAVE =
>> + 1U << PERF_SAMPLE_BRANCH_TYPE_SAVE_SHIFT,
>> +
>> PERF_SAMPLE_BRANCH_MAX = 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
>> };
>>
>> +/*
>> + * Common flow change classification
>> + */
>> +enum {
>> + PERF_BR_NONE = 0, /* unknown */
>> + PERF_BR_JCC = 1, /* conditional jump */
>> + PERF_BR_JMP = 2, /* jump */
>> + PERF_BR_IND_JMP = 3, /* indirect jump */
>> + PERF_BR_CALL = 4, /* call */
>> + PERF_BR_IND_CALL = 5, /* indirect call */
>> + PERF_BR_RET = 6, /* return */
>> + PERF_BR_SYSCALL = 7, /* syscall */
>> + PERF_BR_SYSRET = 8, /* syscall return */
>> + PERF_BR_IRQ = 9, /* hw interrupt/trap/fault */
>> + PERF_BR_INT = 10, /* sw interrupt */
>> + PERF_BR_IRET = 11, /* return from interrupt */
>> + PERF_BR_FAR_BRANCH = 12, /* not generic far branch type */
>> + PERF_BR_MAX,
>> +};
>> +
>> #define PERF_SAMPLE_BRANCH_PLM_ALL \
>> (PERF_SAMPLE_BRANCH_USER|\
>> PERF_SAMPLE_BRANCH_KERNEL|\
>> @@ -999,6 +1024,7 @@ union perf_mem_data_src {
>> * in_tx: running in a hardware transaction
>> * abort: aborting a hardware transaction
>> * cycles: cycles from last branch (or 0 if not supported)
>> + * type: branch type
>> */
>> struct perf_branch_entry {
>> __u64 from;
>> @@ -1008,7 +1034,8 @@ struct perf_branch_entry {
>> in_tx:1, /* in transaction */
>> abort:1, /* transaction abort */
>> cycles:16, /* cycle count to last branch */
>> - reserved:44;
>> + type:4, /* branch type */
>> + reserved:40;
>> };
>>
>> #endif /* _UAPI_LINUX_PERF_EVENT_H */
>> --
>> 2.7.4
>>
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