From b0e878759452314676fbdd71df4ac67e7d08de5d Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 28 Aug 2015 14:06:07 +0200 Subject: perf/abi: Document some more aspects of the perf ABI Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 105 +++++++++++++++++++++++++++++++++++++++------ 1 file changed, 92 insertions(+), 13 deletions(-) (limited to 'include/linux') diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 092a0e8a479a..d61ee4459eee 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -140,27 +140,60 @@ struct hw_perf_event { }; #endif }; + /* + * If the event is a per task event, this will point to the task in + * question. See the comment in perf_event_alloc(). + */ struct task_struct *target; + +/* + * hw_perf_event::state flags; used to track the PERF_EF_* state. + */ +#define PERF_HES_STOPPED 0x01 /* the counter is stopped */ +#define PERF_HES_UPTODATE 0x02 /* event->count up-to-date */ +#define PERF_HES_ARCH 0x04 + int state; + + /* + * The last observed hardware counter value, updated with a + * local64_cmpxchg() such that pmu::read() can be called nested. + */ local64_t prev_count; + + /* + * The period to start the next sample with. + */ u64 sample_period; + + /* + * The period we started this sample with. + */ u64 last_period; + + /* + * However much is left of the current period; note that this is + * a full 64bit value and allows for generation of periods longer + * than hardware might allow. + */ local64_t period_left; + + /* + * State for throttling the event, see __perf_event_overflow() and + * perf_adjust_freq_unthr_context(). + */ u64 interrupts_seq; u64 interrupts; + /* + * State for freq target events, see __perf_event_overflow() and + * perf_adjust_freq_unthr_context(). + */ u64 freq_time_stamp; u64 freq_count_stamp; #endif }; -/* - * hw_perf_event::state flags - */ -#define PERF_HES_STOPPED 0x01 /* the counter is stopped */ -#define PERF_HES_UPTODATE 0x02 /* event->count up-to-date */ -#define PERF_HES_ARCH 0x04 - struct perf_event; /* @@ -210,7 +243,19 @@ struct pmu { /* * Try and initialize the event for this PMU. - * Should return -ENOENT when the @event doesn't match this PMU. + * + * Returns: + * -ENOENT -- @event is not for this PMU + * + * -ENODEV -- @event is for this PMU but PMU not present + * -EBUSY -- @event is for this PMU but PMU temporarily unavailable + * -EINVAL -- @event is for this PMU but @event is not valid + * -EOPNOTSUPP -- @event is for this PMU, @event is valid, but not supported + * -EACCESS -- @event is for this PMU, @event is valid, but no privilidges + * + * 0 -- @event is for this PMU and valid + * + * Other error return values are allowed. */ int (*event_init) (struct perf_event *event); @@ -221,27 +266,61 @@ struct pmu { void (*event_mapped) (struct perf_event *event); /*optional*/ void (*event_unmapped) (struct perf_event *event); /*optional*/ + /* + * Flags for ->add()/->del()/ ->start()/->stop(). There are + * matching hw_perf_event::state flags. + */ #define PERF_EF_START 0x01 /* start the counter when adding */ #define PERF_EF_RELOAD 0x02 /* reload the counter when starting */ #define PERF_EF_UPDATE 0x04 /* update the counter when stopping */ /* - * Adds/Removes a counter to/from the PMU, can be done inside - * a transaction, see the ->*_txn() methods. + * Adds/Removes a counter to/from the PMU, can be done inside a + * transaction, see the ->*_txn() methods. + * + * The add/del callbacks will reserve all hardware resources required + * to service the event, this includes any counter constraint + * scheduling etc. + * + * Called with IRQs disabled and the PMU disabled on the CPU the event + * is on. + * + * ->add() called without PERF_EF_START should result in the same state + * as ->add() followed by ->stop(). + * + * ->del() must always PERF_EF_UPDATE stop an event. If it calls + * ->stop() that must deal with already being stopped without + * PERF_EF_UPDATE. */ int (*add) (struct perf_event *event, int flags); void (*del) (struct perf_event *event, int flags); /* - * Starts/Stops a counter present on the PMU. The PMI handler - * should stop the counter when perf_event_overflow() returns - * !0. ->start() will be used to continue. + * Starts/Stops a counter present on the PMU. + * + * The PMI handler should stop the counter when perf_event_overflow() + * returns !0. ->start() will be used to continue. + * + * Also used to change the sample period. + * + * Called with IRQs disabled and the PMU disabled on the CPU the event + * is on -- will be called from NMI context with the PMU generates + * NMIs. + * + * ->stop() with PERF_EF_UPDATE will read the counter and update + * period/count values like ->read() would. + * + * ->start() with PERF_EF_RELOAD will reprogram the the counter + * value, must be preceded by a ->stop() with PERF_EF_UPDATE. */ void (*start) (struct perf_event *event, int flags); void (*stop) (struct perf_event *event, int flags); /* * Updates the counter value of the event. + * + * For sampling capable PMUs this will also update the software period + * hw_perf_event::period_left field. */ void (*read) (struct perf_event *event); -- cgit From fbbe07011581990ef74dfac06dc8511b1a14badb Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu Date: Thu, 3 Sep 2015 20:07:45 -0700 Subject: perf/core: Add a 'flags' parameter to the PMU transactional interfaces Currently, the PMU interface allows reading only one counter at a time. But some PMUs like the 24x7 counters in Power, support reading several counters at once. To leveage this functionality, extend the transaction interface to support a "transaction type". The first type, PERF_PMU_TXN_ADD, refers to the existing transactions, i.e. used to _schedule_ all the events on the PMU as a group. A second transaction type, PERF_PMU_TXN_READ, will be used in a follow-on patch, by the 24x7 counters to read several counters at once. Extend the transaction interfaces to the PMU to accept a 'txn_flags' parameter and use this parameter to ignore any transactions that are not of type PERF_PMU_TXN_ADD. Thanks to Peter Zijlstra for his input. Signed-off-by: Sukadev Bhattiprolu [peterz: s390 compile fix] Signed-off-by: Peter Zijlstra (Intel) Acked-by: Michael Ellerman Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Link: http://lkml.kernel.org/r/1441336073-22750-3-git-send-email-sukadev@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index d61ee4459eee..ea3b5dd21a4c 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -201,6 +201,8 @@ struct perf_event; */ #define PERF_EVENT_TXN 0x1 +#define PERF_PMU_TXN_ADD 0x1 /* txn to add/schedule event on PMU */ + /** * pmu::capabilities flags */ @@ -331,20 +333,26 @@ struct pmu { * * Start the transaction, after this ->add() doesn't need to * do schedulability tests. + * + * Optional. */ - void (*start_txn) (struct pmu *pmu); /* optional */ + void (*start_txn) (struct pmu *pmu, unsigned int txn_flags); /* * If ->start_txn() disabled the ->add() schedulability test * then ->commit_txn() is required to perform one. On success * the transaction is closed. On error the transaction is kept * open until ->cancel_txn() is called. + * + * Optional. */ - int (*commit_txn) (struct pmu *pmu); /* optional */ + int (*commit_txn) (struct pmu *pmu); /* * Will cancel the transaction, assumes ->del() is called * for each successful ->add() during the transaction. + * + * Optional. */ - void (*cancel_txn) (struct pmu *pmu); /* optional */ + void (*cancel_txn) (struct pmu *pmu); /* * Will return the value for perf_event_mmap_page::index for this event, -- cgit From 4a00c16e552ea5e71756cd29cd2df7557ec9cac4 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu Date: Thu, 3 Sep 2015 20:07:51 -0700 Subject: perf/core: Define PERF_PMU_TXN_READ interface Define a new PERF_PMU_TXN_READ interface to read a group of counters at once. pmu->start_txn() // Initialize before first event for each event in group pmu->read(event); // Queue each event to be read rc = pmu->commit_txn() // Read/update all queued counters Note that we use this interface with all PMUs. PMUs that implement this interface use the ->read() operation to _queue_ the counters to be read and use ->commit_txn() to actually read all the queued counters at once. PMUs that don't implement PERF_PMU_TXN_READ ignore ->start_txn() and ->commit_txn() and continue to read counters one at a time. Thanks to input from Peter Zijlstra. Signed-off-by: Sukadev Bhattiprolu Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Michael Ellerman Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Link: http://lkml.kernel.org/r/1441336073-22750-9-git-send-email-sukadev@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index ea3b5dd21a4c..b83cea932f74 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -202,6 +202,7 @@ struct perf_event; #define PERF_EVENT_TXN 0x1 #define PERF_PMU_TXN_ADD 0x1 /* txn to add/schedule event on PMU */ +#define PERF_PMU_TXN_READ 0x2 /* txn to read event group from PMU */ /** * pmu::capabilities flags -- cgit From 8f3e5684d3fbd91ead283916676fa3dac22615e5 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu Date: Thu, 3 Sep 2015 20:07:53 -0700 Subject: perf/core: Drop PERF_EVENT_TXN We currently use PERF_EVENT_TXN flag to determine if we are in the middle of a transaction. If in a transaction, we defer the schedulability checks from pmu->add() operation to the pmu->commit() operation. Now that we have "transaction types" (PERF_PMU_TXN_ADD, PERF_PMU_TXN_READ) we can use the type to determine if we are in a transaction and drop the PERF_EVENT_TXN flag. When PERF_EVENT_TXN is dropped, the cpuhw->group_flag on some architectures becomes unused, so drop that field as well. This is an extension of the Powerpc patch from Peter Zijlstra to s390, Sparc and x86 architectures. Signed-off-by: Sukadev Bhattiprolu Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Michael Ellerman Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Link: http://lkml.kernel.org/r/1441336073-22750-11-git-send-email-sukadev@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index b83cea932f74..d841d33bcdc9 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -199,8 +199,6 @@ struct perf_event; /* * Common implementation detail of pmu::{start,commit,cancel}_txn */ -#define PERF_EVENT_TXN 0x1 - #define PERF_PMU_TXN_ADD 0x1 /* txn to add/schedule event on PMU */ #define PERF_PMU_TXN_READ 0x2 /* txn to read event group from PMU */ -- cgit