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Date: Thu, 17 Apr 2014 14:44:26 +0200 From: Jean Pihet <jean.pihet@...aro.org> To: Borislav Petkov <bp@...en8.de>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Arnaldo Carvalho de Melo <acme@...radead.org>, Jiri Olsa <jolsa@...hat.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Robert Richter <rric@...nel.org> Cc: Jean Pihet <jean.pihet@...aro.org> Subject: Re: [PATCH v4 00/16] perf, persistent: Add persistent events Hi, Ping on this series. Are there some opinions or interest in this? Regards, Jean On 7 April 2014 17:04, Jean Pihet <jean.pihet@...aro.org> wrote: > Jean Pihet <jean.pihet@...aro.org>: > - In order to restart the discussion on the topic, here is a rebased > version of Robert's latest patches (v3) on acme/perf/core. > It has been compiled and lightly tested on ARM64. > > - From the latest discussion on ML the ioctls are renamed from > PERF_EVENT_IOC_ATTACH/DETACH to PERF_EVENT_IOC_CLAIM/UNCLAIM. > > > Robert Richter <rric@...nel.org>: > This patch set implements the necessary kernel changes for persistent > events. > > Persistent events run standalone in the system without the need of a > controlling process that holds an event's file descriptor. The events > are always enabled and collect data samples in a ring buffer. > Processes may connect to existing persistent events using the > perf_event_open() syscall. For this the syscall must be configured > using the new PERF_TYPE_PERSISTENT event type and a unique event > identifier specified in attr.config. The id is propagated in sysfs or > using ioctl (see below). > > Persistent event buffers may be accessed with mmap() in the same way > as for any other event. Since the buffers may be used by multiple > processes at the same time, there is only read-only access to them. > Currently there is only support for per-cpu events, thus root access > is needed too. > > Persistent events are visible in sysfs. They are added or removed > dynamically. With the information in sysfs userland knows about how to > setup the perf_event attribute of a persistent event. Since a > persistent event always has the persistent flag set, a way is needed > to express this in sysfs. A new syntax is used for this. With > 'attr<num>:<mask>' any bit in the attribute structure may be set in a > similar way as using 'config<num>', but <num> is an index that points > to the u64 value to change within the attribute. > > For persistent events the persistent flag (bit 24 of flag field in > struct perf_event_attr) needs to be set which is expressed in sysfs > with "attr5:24". E.g. the mce_record event is described in sysfs as > follows: > > /sys/bus/event_source/devices/persistent/events/mce_record:persistent,config=106 > /sys/bus/event_source/devices/persistent/format/persistent:attr5:24 > > Note that perf tools need to support the 'attr<num>' syntax that is > added in a separate patch set. With it we are able to run perf tool > commands to read persistent events, e.g.: > > # perf record -e persistent/mce_record/ sleep 10 > # perf top -e persistent/mce_record/ > > In general the new syntax is flexible to describe with sysfs any event > to be setup by perf tools. > > There are ioctl functions to control persistent events that can be > used to detach or attach an event to or from a process. The > PERF_EVENT_IOC_UNCLAIM ioctl call makes an event persistent. The > perf_event_open() syscall can be used to re-open the event by any > process. The PERF_EVENT_IOC_CLAIM ioctl attaches the event again so > that it is removed after closing the event's fd. > > The patches base on the originally work from Borislav Petkov. > > This version 3 of the patch set is a complete rework of the code. > There are the following major changes: > > * new event type PERF_TYPE_PERSISTENT introduced, > > * support for all type of events, > > * unique event ids, > > * improvements in reference counting and locking, > > * ioctl functions are added to control persistency, > > * the sysfs implementation now uses variable list size. > > This should address most issues discussed during last review of > version 2. The following is unresolved yet and can be added later on > top of this patches, if necessary: > > * support for per-task events (also allowing non-root access), > > * creation of persistent events for disabled cpus, > > * make event persistent with already open (mmap'ed) buffers, > > * make event persistent while creating it. > > First patches contain some rework of the perf mmap code to reuse it > for persistent events. > > Also note that patch 12 (ioctl functions to control persistency) is > RFC and untested. A perf tools implementation for this is missing and > some ideas are needed how this could be integrated, esp. in something > like perf trace or so. > > All v3 patches can be found here: > > git://git.kernel.org/pub/scm/linux/kernel/git/rric/oprofile.git persistent-v3 > > Note: I will resent the perf tools patch necessary to use persistent > events. > > -Robert > > > Borislav Petkov (1): > mce, x86: Enable persistent events > > Robert Richter (15): > perf, mmap: Factor out ring_buffer_detach_all() > perf, mmap: Factor out try_get_event()/put_event() > perf, mmap: Factor out perf_alloc/free_rb() > perf, mmap: Factor out perf_get_fd() > perf: Add persistent events > perf, persistent: Implementing a persistent pmu > perf, persistent: Exposing persistent events using sysfs > perf, persistent: Use unique event ids > perf, persistent: Implement reference counter for events > perf, persistent: Dynamically resize list of sysfs entries > perf, persistent: ioctl functions to control persistency > perf tools: Rename flex conditions to avoid name conflicts > perf tools: Modify event parser to update event attribute by index > perf tools: Add attr<num> syntax to event parser > perf tools: Retry mapping buffers readonly on EACCES > > .../testing/sysfs-bus-event_source-devices-format | 43 +- > arch/x86/kernel/cpu/mcheck/mce.c | 19 + > include/linux/perf_event.h | 12 +- > include/uapi/linux/perf_event.h | 6 +- > kernel/events/Makefile | 2 +- > kernel/events/core.c | 214 +++++--- > kernel/events/internal.h | 20 + > kernel/events/persistent.c | 563 +++++++++++++++++++++ > tools/perf/builtin-record.c | 11 +- > tools/perf/builtin-top.c | 8 +- > tools/perf/perf.h | 1 + > tools/perf/tests/parse-events.c | 12 +- > tools/perf/util/parse-events.c | 59 +-- > tools/perf/util/parse-events.h | 12 +- > tools/perf/util/parse-events.l | 58 ++- > tools/perf/util/parse-events.y | 24 +- > tools/perf/util/pmu.c | 32 +- > tools/perf/util/pmu.h | 9 +- > tools/perf/util/pmu.l | 1 + > tools/perf/util/pmu.y | 18 +- > 20 files changed, 911 insertions(+), 213 deletions(-) > create mode 100644 kernel/events/persistent.c > > -- > 1.7.11.7 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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