Date:	Tue, 21 Jul 2015 09:18:52 -0500
From:	Tom Zanussi <tom.zanussi@...ux.intel.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	rostedt@...dmis.org, daniel.wagner@...-carit.de,
	namhyung@...nel.org, josh@...htriplett.org, andi@...stfloor.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 00/22] tracing: 'hist' triggers

On Tue, 2015-07-21 at 18:40 +0900, Masami Hiramatsu wrote:
> Hi Tom,
> 
> Thank you for updating your patches, I'm testing it.
> 
> And when I'm testing hist trigger, I've found that the .hex modifiers on value
> doesn't work, but no semantic error.
> 

Yeah, the hex modifier on values got dropped when refactoring the
patchset, will fix.  Thanks for testing and pointing it out.

Tom

> [root@...alhost tracing]# echo 'hist:keys=parent_pid:vals=common_pid.hex' > events/sched/sched_process_fork/trigger
> [root@...alhost tracing]#
> 
> [root@...alhost tracing]# cat events/sched/sched_process_fork/hist
> # trigger info: hist:keys=parent_pid:vals=hitcount,common_pid.hex:sort=hitcount:size=2048 [active]
> 
> { parent_pid:      26582 } hitcount:          1  common_pid:      26582
> { parent_pid:      11968 } hitcount:          1  common_pid:      11968
> { parent_pid:      11956 } hitcount:          2  common_pid:      23912
> 
> Totals:
>     Hits: 4
>     Entries: 3
>     Dropped: 0
> 
> while other modifiers return -EINVAL.
> 
> [root@...alhost tracing]# echo 'hist:keys=parent_pid:vals=common_pid.execname' > events/sched/sched_process_fork/trigger
> -bash: echo: write error: Invalid argument
> 
> Thank you,
> 
> On 2015/07/17 2:22, Tom Zanussi wrote:
> > This is v9 of the 'hist triggers' patchset.
> > 
> > Changes from v8:
> > 
> > Same as v8, but with the RFC patch [ftrace: Add function_hist tracer]
> > removed, and rebased to latest trace/for-next.
> > 
> > Changes from v7:
> > 
> > This version refactors the commits as suggested by Masami.  There are
> > now more commits, but the result should be much more reviewable.  The
> > ending code is the same as before, modulo a couple minor bug fixes I
> > discovered while refactoring and testing.
> > 
> > I've also reviewed and fixed a number of shortcomings and errors in
> > the comments, and have added a new discussion of the tracing_map data
> > structures after Steve mentioned he found them confusing and/or
> > insufficiently documented.
> > 
> > Also, I kept Namhyung's string patch [tracing: Support string type key
> > properly] as submitted, but added a follow-on patch that refactors it
> > and fixes a problem I found with it that enabled static string keys to
> > contain random chars and therefore incorrect map insertions.
> > 
> > Changes from v6:
> > 
> > This version adds a new 'sym-offset' modifier as requested by Masami.
> > I implemented it as a modifier rather than using the trace option as
> > suggested, in part because I wanted to keep it all self-contained and
> > it seemed more consistent to just add it alongside the 'sym' modifier.
> > Also, hist triggers arent't really a tracer and therefore don't
> > directly tie into the option update/callback mechanism so making use
> > of it isn't as simple as a normal tracer.
> > 
> > I also changed the sort key specification to be stricter and signal an
> > error if the specified sort key wasn't found (rather than defaulting
> > to hitcount in those cases), also suggested by Masami.  Thanks,
> > Masami, for your input!
> > 
> > Also updated the Documentation and tracing/README to reflect the
> > changes.
> > 
> > Changes from v5:
> > 
> > This version adds support for compound keys, along with the related
> > ability to sort using primary and secondary keys.  This was mentioned
> > in previous versions as the last important piece that remained
> > unimplemented, and is now implemented.  (I didn't have time to get to
> > the couple of enhancements suggested by Masami, but I expect to be
> > able to add those later on top of these.)
> > 
> > Because we now support compound keys and it's not immediately clear in
> > the output exactly which fields correspond to keys, the key(s),
> > compound or not, are now enclosed by curly braces.
> > 
> > The Documentation and README have been updated to reflect the changes,
> > and several new examples have been added to illustrate how to use
> > compound keys.
> > 
> > Also, the code was updated to work with the new ftrace_event_file,
> > etc, renaming in tracing/for-next.
> > 
> > Changes from v4:
> > 
> > This version addresses some problems and suggestions made by Daniel
> > Wagner - a lot of the code was reworked to get rid of the distinction
> > between keys and values, and as a result, both keys and values can be
> > used as sort keys.  As suggested, it also allows 'val=' to be absent
> > in a trigger command - if no 'val' is specified, hitcount is assumed
> > and automatically used as the only val.
> > 
> > The map code was also separated out into a separate file,
> > tracing_map.c, allowing it to be reused.  It also adds a second tracer
> > called function_hist that actually does reuse the code, as an RFC
> > patch.
> > 
> > Patch 01/10 [tracing: Update cond flag when enabling or disabling..]
> > is a fix for a problem noticed by Daniel and that fixes a problem in
> > existing trigger code and should be applied regardless of whether the
> > rest of the patchset is merged.
> > 
> > As mentioned, patch 10/10 is an RFC patch implementing a new tracer
> > based on the function tracer code.  It's a fun little tool and is
> > useful for a specific problem I'm working on (and is also a nice test
> > of the tracing_map code), but is an RFC because first, I'm not sure it
> > would really be of general interest and secondly, it's POC-level
> > quality and I'd need to spend more time fixing it up to make it
> > upstreamable, but I don't want to waste my time if not.
> > 
> > There are a couple of important bits of functionality that were
> > present in v1 but not yet reimplemented in v5.
> > 
> > The first is support for compound keys.  Currently, maps can only be
> > keyed on a single event field, whereas in v1 they could be keyed on
> > multiple keys.  With support for compound keys, you can create much
> > more interesting output, such as for example per-pid lists of
> > syscalls or read counts e.g.:
> > 
> >   # echo 'hist:keys=common_pid.execname,id.syscall:vals=hitcount' > \
> >         /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
> > 
> >   # cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist
> > 
> >   key: common_pid:bash[3112], id:sys_write		       vals: count:69
> >   key: common_pid:bash[3112], id:sys_rt_sigprocmask	       vals: count:218
> > 
> >   key: common_pid:update-notifier[3164], id:sys_poll	       vals: count:37
> >   key: common_pid:update-notifier[3164], id:sys_recvfrom       vals: count:118
> > 
> >   key: common_pid:deja-dup-monito[3194], id:sys_sendto	       vals: count:1
> >   key: common_pid:deja-dup-monito[3194], id:sys_read	       vals: count:4
> >   key: common_pid:deja-dup-monito[3194], id:sys_poll	       vals: count:8
> >   key: common_pid:deja-dup-monito[3194], id:sys_recvmsg	       vals: count:8
> >   key: common_pid:deja-dup-monito[3194], id:sys_getegid	       vals: count:8
> > 
> >   key: common_pid:emacs[3275], id:sys_fsync		       vals: count:1
> >   key: common_pid:emacs[3275], id:sys_open		       vals: count:1
> >   key: common_pid:emacs[3275], id:sys_symlink		       vals: count:2
> >   key: common_pid:emacs[3275], id:sys_poll		       vals: count:23
> >   key: common_pid:emacs[3275], id:sys_select		       vals: count:23
> >   key: common_pid:emacs[3275], id:unknown_syscall	       vals: count:34
> >   key: common_pid:emacs[3275], id:sys_ioctl		       vals: count:60
> >   key: common_pid:emacs[3275], id:sys_rt_sigprocmask	       vals: count:116
> > 
> >   key: common_pid:cat[3323], id:sys_munmap		       vals: count:1
> >   key: common_pid:cat[3323], id:sys_fadvise64		       vals: count:1
> > 
> > Related to that is support for sorting on multiple fields.  Currently,
> > you can sort using only a primary key.  Being able to sort on multiple
> > or at least a secondary key is indispensible for seeing trends when
> > displaying multiple values.
> > 
> > Changes from v3:
> > 
> > v4 fixes the race in tracing_map_insert() noted in v3, where
> > map.val.key could be checked even if map.val wasn't yet set.  The
> > simple fix for that in tracing_map_insert() introduces the possibility
> > of duplicates in the map, which though rare, need to be accounted for
> > in the output.  To address that, duplicate-merging code was added to
> > the map-printing code.
> > 
> > It was also pointed out that it didn't seem correct to include
> > module.h, but the fix for that has deeper roots and is being addressed
> > by a separate patchset; for now we need to continue including
> > module.h, though prompted by that I did some other header include
> > cleanup.
> > 
> > The functionality remains the same as v2, but this version no longer
> > tries to export and use bpf_maps, and more importantly removes the
> > associated GFP_NOTRACE/trace event hacks and kmem macros required to
> > work around the bpf_map implementation.
> > 
> > The tracing_map functionality is instead built on top of a simple
> > lock-free map algorithm originated by Dr. Cliff Click (see references
> > in the code for more details), which though too restrictive to be
> > general-purpose in its current form, functions nicely as a
> > special-purpose tracing map.
> > 
> > v3 also moves the hist triggers code into a separate file and puts it
> > all behind a new config option, CONFIG_HIST_TRIGGERS.  It also merges
> > in the sorting code rather than keeping it as a separate patch.
> > 
> > This patchset also includes a couple other new and related triggers,
> > enable_hist and disable_hist, very similar to the existing
> > enable_event/disable_event triggers used to automatically enable and
> > disable events based on a triggering condition, but in this case
> > allowing hist triggers to be enabled and disabled in the same way.
> > 
> >  - Added an insert check for val before checking the key associated with val
> >  - Added code to merge possible duplicates in the map
> > 
> > Changes from v2:
> >  - reimplemented tracing_map, replacing bpf_map with nmi-safe/lock-free map
> >  - removed GPF_NOTRACE, kmalloc/free macros and event hacks needed by bpf_maps
> >  - moved hist triggers from trace_events_trigger.c to trace_events_hist.c
> >  - added CONFIG_HIST_TRIGGERS config option
> >  - consolidated sorting code with main patch
> > 
> > Changes from v1:
> >  - completely rewritten on top of tracing_map (renamed and exported bpf_map)
> >  - added map clearing and client ops to tracing_map
> >  - changed the name from 'hash' triggers to 'hist' triggers
> >  - added new trigger 'pause' feature
> >  - added new enable_hist and disable_hist triggers
> >  - added usage for hist/enable_hist/disable hist to tracing/README
> >  - moved examples into Documentation/trace/event.txt
> >  - added ___GFP_NOTRACE, kmalloc/kfree macros, and conditional kmem tracepoints
> > 
> > The following changes since commit b44754d8262d3aab842998cf747f44fe6090be9f:
> > 
> >   ring_buffer: Allow to exit the ring buffer benchmark immediately (2015-06-15 12:03:12 -0400)
> > 
> > are available in the git repository at:
> > 
> >   git://git.yoctoproject.org/linux-yocto-contrib.git tzanussi/hist-triggers-v9
> >   http://git.yoctoproject.org/cgit/cgit.cgi/linux-yocto-contrib/log/?h=tzanussi/hist-triggers-v9
> > 
> > Namhyung Kim (1):
> >   tracing: Support string type key properly
> > 
> > Tom Zanussi (21):
> >   tracing: Update cond flag when enabling or disabling a trigger
> >   tracing: Make ftrace_event_field checking functions available
> >   tracing: Make event trigger functions available
> >   tracing: Add event record param to trigger_ops.func()
> >   tracing: Add get_syscall_name()
> >   tracing: Add a per-event-trigger 'paused' field
> >   tracing: Add lock-free tracing_map
> >   tracing: Add 'hist' event trigger command
> >   tracing: Add hist trigger support for multiple values ('vals=' param)
> >   tracing: Add hist trigger support for compound keys
> >   tracing: Add hist trigger support for user-defined sorting ('sort='
> >     param)
> >   tracing: Add hist trigger support for pausing and continuing a trace
> >   tracing: Add hist trigger support for clearing a trace
> >   tracing: Add hist trigger 'hex' modifier for displaying numeric fields
> >   tracing: Add hist trigger 'sym' and 'sym-offset' modifiers
> >   tracing: Add hist trigger 'execname' modifier
> >   tracing: Add hist trigger 'syscall' modifier
> >   tracing: Add hist trigger support for stacktraces as keys
> >   tracing: Remove restriction on string position in hist trigger keys
> >   tracing: Add enable_hist/disable_hist triggers
> >   tracing: Add 'hist' trigger Documentation
> > 
> >  Documentation/trace/events.txt      | 1131 +++++++++++++++++++++++++++
> >  include/linux/trace_events.h        |    9 +-
> >  kernel/trace/Kconfig                |   14 +
> >  kernel/trace/Makefile               |    2 +
> >  kernel/trace/trace.c                |   66 ++
> >  kernel/trace/trace.h                |   77 +-
> >  kernel/trace/trace_events.c         |    4 +
> >  kernel/trace/trace_events_filter.c  |   12 -
> >  kernel/trace/trace_events_hist.c    | 1462 +++++++++++++++++++++++++++++++++++
> >  kernel/trace/trace_events_trigger.c |  149 ++--
> >  kernel/trace/trace_syscalls.c       |   11 +
> >  kernel/trace/tracing_map.c          |  935 ++++++++++++++++++++++
> >  kernel/trace/tracing_map.h          |  258 +++++++
> >  13 files changed, 4046 insertions(+), 84 deletions(-)
> >  create mode 100644 kernel/trace/trace_events_hist.c
> >  create mode 100644 kernel/trace/tracing_map.c
> >  create mode 100644 kernel/trace/tracing_map.h
> > 
> 
> 


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