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SubjectRe: [RFC 0/5] perf: Create hist_entry groups
On Tue, Apr 15, 2014 at 12:01:50PM +0900, Namhyung Kim wrote:
> Hi Don,
> On Thu, 10 Apr 2014 16:10:56 -0400, Don Zickus wrote:
> > This patchset creates a new layer of hist entry objects called
> > hist_entry_groups. The purpose is to help organize the hist_entries
> > into groups before sorting them. As a result you can gain a
> > new perspective on the data by organizing the groups into cpu, pid
> > or cacheline. See patch 5 for sample output.
> >
> > The main driver for this patchset is to find a way to sort and display
> > cacheline data in a way that is useful. My previous attempts seemed
> > hackish until I realized cacheline sorting is really just a collection
> > of hist_entries. Anyway that was my focus for doing this.
> >
> > The overall idea looks like:
> >
> > evlist
> > evsel
> > hists
> > hist_entry_group <<< new object
> > hist_entry
> >
> >
> > Implementing this was not pretty. I tried to seperate the patches the
> > best I could. But in order for each patch to compile, patch 4 turned into
> > a 1400 line diff that is mostly noise.
> >
> > Also, this patchset breaks most tools (mainly because I don't understand
> > all the interactions), hence the RFC. I mostly tested with 'perf report
> > --stdio' and 'perf mem report --stdio'.
> >
> > Please let me know if this is an interesting idea to go forward with or not.
> I'd like to show you my previous two patchsets.
> The first one is for adding --field option and changing the sort
> behavior little different [1]. I'm about to send a new version to the
> list soon.
> I think what you want to do is sorting output by an order of sort keys
> not just by the overhead. So with the patchset applied, you can do it
> like:
> $ perf report --field overhead,pid,dso,sym --sort pid
> # Overhead Command: Pid Shared Object
> # ........ .................... ................. ...........................
> #
> 32.93% swapper: 0 [kernel.kallsyms] [k] intel_idle
> 6.79% swapper: 0 [kernel.kallsyms] [k] enqueue_entity
> 1.42% swapper: 0 [kernel.kallsyms] [k] update_sd_lb_stats
> 1.30% swapper: 0 [kernel.kallsyms] [k] timekeeping_max_deferme
> 1.18% swapper: 0 [kernel.kallsyms] [k] update_cfs_shares
> 1.07% swapper: 0 [kernel.kallsyms] [k] __irq_work_run
> 0.96% swapper: 0 [kernel.kallsyms] [k] rcu_check_callbacks
> 0.64% swapper: 0 [kernel.kallsyms] [k] irqtime_account_process
> 0.50% swapper: 0 [kernel.kallsyms] [k] int_sqrt
> 0.47% swapper: 0 [kernel.kallsyms] [k] __tick_nohz_idle_enter
> 0.47% swapper: 0 [kernel.kallsyms] [k] menu_select
> 0.35% swapper: 0 [kernel.kallsyms] [k] run_timer_softirq
> 0.16% swapper: 0 [kernel.kallsyms] [k] __perf_event_enable
> 0.12% swapper: 0 [kernel.kallsyms] [k] rcu_eqs_exit_common.isr
> 0.50% watchdog/6: 37 [kernel.kallsyms] [k] update_sd_lb_stats
> 3.45% Xorg: 1335 [kernel.kallsyms] [k] schedule
> 6.55% gnome-terminal: 1903 [.] __strcmp_sse42
> 1.59% firefox: 2137 [kernel.kallsyms] [k] cpuacct_charge
> 0.50% emacs: 2473 emacs-24.1 [.] 0x000000000012241a
> 0.38% emacs: 2473 emacs-24.1 [.] 0x00000000000bfbf7
> 0.31% emacs: 2473 emacs-24.1 [.] 0x00000000001780dd
> 0.29% emacs: 2473 emacs-24.1 [.] 0x000000000002eb48
> 4.40% kworker/7:1:11028 [kernel.kallsyms] [k] generic_exec_single
> 1.30% kworker/0:0:25667 [kernel.kallsyms] [k] generic_exec_single
> 5.93% kworker/5:1:26447 [kernel.kallsyms] [k] generic_exec_single
> 2.06% kworker/1:2:26653 [kernel.kallsyms] [k] generic_exec_single
> As you can see the output is now sorted by pid value (and then overhead,
> dso, sym if previous key resulted in a same value), so swapper (pid 0)
> comes first and then watchdog/6, Xorg, and so on..

This is probably a workable solution for our c2c tool. I can play with
this some more.

> But it's not guarantee that the hottest pid comes always first on the
> output, it just sorted it by pid and it gets the result simply because
> the system was idle mostly. I think you can handle it in your c2c tool
> properly though.
> Another one I'd like to introduce is somewhat similar to your work.
> It's called hierarchy view and groups each entries according to sort
> keys [2]. But it only supported --gtk output at that time (in order not
> to make the hands dirty unnecessarily ;-) and (thus?) didn't get much
> review. But I think the idea is same and requires less change by just
> adding few fields (rb_root) to hist_entry instead of new data structure.

Looks promising.

I keep thinking with all these hist_entry hacks to support flexibility, if
we should just do some bigger changes to the design. I was thinking along
the lines of combining hist_entries and callchain stuff and maybe output
changes into a unified heirarchy somehow. This way we could re-use alot
of code and throw away all the silly callchain special cases and just
treat it like a sort_entry.

I am not sure how that would work (or if really possible), but I was
playing with ideas in my head based on Jiri's suggestion, of something
like a tree layout where 'struct hists' would be sorta like a directory
and would dictate the data type in the 'files' of 'struct hist_entry'.

The idea was 'struct hists' would normally have a HIST data type and
contain the specific sort_entry(ies) for its heirarchy. The 'struct
hist_entries' below it would all be the normal HIST data type. For
callchain support, there would be a 'struct hist' under each 'hist_entry'
that would be of data type CALLCHAIN and its sort specific rules.

This way we could add display a callchain anywhere in the heirarchy
(instead of the normal last position).

If you then split the entries and entries_in out of struct hist and
instead create two 'struct hists', one for input and one output. Then
perhaps we could create a data type GTK_OUT for a gtk specific output sort
of entries. This might help re-use/reduce some of the ui/ code.

Anyway, it is probably way to much thrashing, just some ideas to help
promote better data visibilty.

I was enjoying the ideas of 'groups' and how it can help re-arrange the
data and allow us to look at bottlenecks differently. While --field and
--hierarchy can achieve similar things, I am wondering if the output is
still simple enough to interpret (and the commandline simple enough for
users to utilize).

My 2cents. Time to jump on a plane.


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