linux-kernel - Re: Scrolling down broken with "perf top --hierarchy"

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Message-ID: <20161010175427.GA8325@x4>
Date:   Mon, 10 Oct 2016 19:54:27 +0200
From:   Markus Trippelsdorf <markus@...ppelsdorf.de>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: Scrolling down broken with "perf top --hierarchy"

On 2016.10.08 at 13:21 +0200, Markus Trippelsdorf wrote:
> On 2016.10.07 at 07:09 +0200, Markus Trippelsdorf wrote:
> > On 2016.10.07 at 06:56 +0200, Markus Trippelsdorf wrote:
> > > On 2016.10.07 at 06:32 +0200, Markus Trippelsdorf wrote:
> > > > On 2016.10.07 at 13:22 +0900, Namhyung Kim wrote:
> > > > > On Fri, Oct 07, 2016 at 05:51:18AM +0200, Markus Trippelsdorf wrote:
> > > > > > On 2016.10.07 at 10:17 +0900, Namhyung Kim wrote:
> > > > > > > On Thu, Oct 06, 2016 at 06:33:33PM +0200, Markus Trippelsdorf wrote:
> > > > > > > > Scrolling down is broken when using "perf top --hierarchy".
> > > > > > > > When it starts up everything is OK and one can scroll up and down to all
> > > > > > > > entries. But as further and further new entries get added to the list,
> > > > > > > > scrolling down is blocked (at the position of the last entry that was
> > > > > > > > shown directly after startup).
> > > > > > > 
> > > > > > > I think below patch will fix the problem.  Please check.
> > > > > > 
> > > > > > Yes. It works fine now. Many thanks.
> > > > > 
> > > > > Good.  Can I add your Tested-by then?
> > > > 
> > > > Sure. 
> > > 
> > > And BTW symbols are currently always cut off at 60 characters in
> > > expanded entries.
> > 
> > Hmm, no. Sometimes they are cut off, sometimes they are not. I haven't
> > figured out what triggered this strange behavior.
> 
> Here is an example:
> 
>  % echo $COLUMNS
>  179
>  % perf top --hierarchy
> +  34.81%     [kernel]
> -  20.89%     chrome
>        0.51%     [.] v8::internal::IncrementalMarking:
>        0.43%     [.] tc_malloc
>        0.29%     [.] sqlite3BtreeMovetoUnpacked
>        0.28%     [.] tc_free
>        0.24%     [.] v8::internal::BodyDescriptorBase:
>        0.24%     [.] sqlite3VdbeExec
>        0.22%     [.] v8::internal::MarkCompactCollecto
>        0.19%     [.] blink::SelectorChecker::checkOne
>        0.19%     [.] SkBlitRow::Color32
>        0.18%     [.] SkBlitLCD16OpaqueRow_SSE2
>        0.17%     [.] btreeInitPage.part.366
>        0.16%     [.] blink::SelectorChecker::matchSele
>        0.15%     [.] blink::ElementRuleCollector::coll
>        0.15%     [.] blink::CSSTokenizer::consumeName
>        0.14%     [.] sqlite3GetVarint
>        0.13%     [.] operator new[]
>        0.12%     [.] FPDFAPI_inflate_fast
>        0.11%     [.] v8::internal::HeapObject::SizeFro
>        0.09%     [.] tracked_objects::ThreadData::Tall
> ...

To continue this monologue, perf doesn't even look at these entries. So some
hists__calc_col_len() calls seem to be missing for the "perf top --hierarchy"
case or hists__reset_col_len() is called too early or too often.

Anyway, the following hack "fixes" the issue for me:

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index b02992efb513..7e468fa56980 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -67,7 +67,7 @@ void hists__calc_col_len(struct hists *hists, struct hist_entry *h)
         * +3 accounts for ' y ' symtab origin info
         */
        if (h->ms.sym) {
-               symlen = h->ms.sym->namelen + 4;
+               symlen = 200;
                if (verbose)
                        symlen += BITS_PER_LONG / 4 + 2 + 3;
                hists__new_col_len(hists, HISTC_SYMBOL, symlen);


-- 
Markus