Date:	Tue, 21 Jul 2015 18:40:12 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Tom Zanussi <tom.zanussi@...ux.intel.com>, rostedt@...dmis.org
CC:	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

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.

[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
> 


-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@...achi.com
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