Messages in this thread | | | From | Namhyung Kim <> | Subject | Re: [PATCHSET 0/8] perf tools: Fix scalability problem on callchain merging (v4) | Date | Fri, 27 Sep 2013 11:08:06 +0900 |
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Hi Ingo,
On Thu, 26 Sep 2013 11:34:26 +0200, Ingo Molnar wrote: > * Namhyung Kim <namhyung@kernel.org> wrote: > >> Hello, >> >> This is a new version of callchain improvement patchset. I found and >> fixed bugs in the previous version. I verified that it produced >> exactly same output before and after applying rbtree conversion patch >> (#1). However after Frederic's new comm infrastructure patches are >> applied it'd be little different. >> >> The patches are on 'perf/callchain-v4' branch in my tree >> >> git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git > > I pulled this into a test-branch and resolved the builtin-trace.c conflict > with tip:master. > > I tried your new code out with Linus's testcase of a parallel kernel > build: > > perf record -g -- make -j8 bzImage > > The 'perf record' session went mostly fine except for lost events: > > Kernel: arch/x86/boot/bzImage is ready (#25) > [ perf record: Woken up 553 times to write data ] > [ perf record: Captured and wrote 196.811 MB perf.data (~8598789 samples) ] > Warning: > Processed 2631982 events and lost 54 chunks! > > Check IO/CPU overload! > > So, for completeness I'll mention that perf fails in two ways here: > > - UI bug: it prints some scary warnings about 'IO/CPU overload' but > does not give any idea what the user could do about it. At minimum it > should print something about increasing --mmap-pages. It should also > print the current value of --mmap-pages so that the user knows to what > value to increase it ... > > - defaults bug: this isn't an extreme workload on an extreme box - it's > a relatively bog standard system with 8 cores and 16 CPUs. The kernel > build was mild as well, with -j8. So losing events in perf record is > absolutely unacceptable. A solution might be to automatically increase > the ring-buffer if -g is used, in expectation of a higher data rate.
Both look sensible. I'll try to cook patches for them.
> > Once perf record was done I had the ~200 MB perf.data - and the 'perf > report' session went much smoother than ever before: the analysis went > very quickly, it finished within 10 seconds and displayed a nice progress > bar. So this is entirely usable IMO. > > One small 'perf report' annoyance is that during the analysis passes > missing symbol printouts flash in the TUI - without the user having a > chance to read them. So those messages should either linger, or be > displayed at a later stage, for example when the user is confronted with > non-resolved symbols like: > > + 28.63% cc1 cc1 [.] 0x00000000006a92cb ◆ > > that is the point where the message would be useful - but nothing > indicates at all that this is an undesirable symbol entry and nothing > helps the user what to do about it! > > A solution might be to display non-intrusive messages about non-resolved > symbols when such a symbol is manipulated (its children are openened, or > annotation is attempted).
Hmm.. I'll think about it more how to do it.
> > Here there is a second annoyance: on the detailed screen the 'annotate' > entry is simply missing when the symbol has not been resolved. If I hit > 'a' on the symbol entry itself in the graph view, then sometimes > annotation works - sometimes it does not and there's no UI feedback > whatsoever why it's not working. > > I'm not suggesting to change the keyboard flow - that is very smooth - but > display information about failed annotations in the status line at the > bottom of the screen would be very useful. Remember: it's _always_ an UI > bug if the user hits a key and absolutely nothing happens. At minimum a > low-key, non-intrusive 'key X not bound' message should appear in the > status line bottom. Deterministic action/reaction sequences are utterly > important when interacting with computers. > > Anyway, very nice progress with the tree here!
Hehe, thanks! Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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