Messages in this thread Patch in this message | | | Date | Fri, 20 Oct 2017 10:39:35 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v6 1/6] perf report: properly handle branch count in match_chain |
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Em Fri, Oct 20, 2017 at 01:38:23PM +0200, Milian Wolff escreveu: > On Freitag, 20. Oktober 2017 12:21:35 CEST Milian Wolff wrote: > > On Donnerstag, 19. Oktober 2017 17:01:08 CEST Namhyung Kim wrote: > > > Hi Andi, > > > > > > On Thu, Oct 19, 2017 at 06:55:19AM -0700, Andi Kleen wrote: > > > > On Thu, Oct 19, 2017 at 12:59:14PM +0200, Milian Wolff wrote: > > > > > On Donnerstag, 19. Oktober 2017 00:41:04 CEST Andi Kleen wrote: > > > > > > Milian Wolff <milian.wolff@kdab.com> writes: > > > > > > > +static enum match_result match_address_dso(struct dso *left_dso, > > > > > > > u64 > > > > > > > left_ip, + struct dso *right_dso, u64 right_ip) > > > > > > > +{ > > > > > > > + if (left_dso == right_dso && left_ip == right_ip) > > > > > > > + return MATCH_EQ; > > > > > > > + else if (left_ip < right_ip) > > > > > > > + return MATCH_LT; > > > > > > > + else > > > > > > > + return MATCH_GT; > > > > > > > +} > > > > > > > > > > > > So why does only the first case check the dso? Does it not matter > > > > > > for the others? > > > > > > > > > > > > Either should be checked by none or by all. > > > > > > > > > > I don't see why it should be checked. It is only required to prevent > > > > > two > > > > > addresses to be considered equal while they are not. So only the one > > > > > check is required, otherwise we return either LT or GT. > > > > > > > > When the comparison is always in the same process (which I think > > > > is not the case) just checking the addresses is sufficient. If they are > > > > not then you always need to check the DSO and only compare inside the > > > > same DSO. > > > > > > As far as I know, the node->ip is a relative address (inside a DSO). > > > So it should compare the dso as well even in the same process. > > > > Sorry guys, I seem to be slow at understanding your review comments. > > > > match_address_dso should impose a sort order on two relative addresses. The > > order should ensure that relative addresses in a different DSO are not > > considered equal. But if the DSOs are different, it doesn't matter whether > > we return LT or GT - or? > > > > Put differently, how would you write this function to take care of the DSO > > in the other two branches? I.e. what to return if the DSOs are different - > > a MATCH_ERROR? > > Thinking a bit more about this. Are you guys maybe hinting at my > implementation breaking the strict ordering rules (is that the right word?). > I.e. a < b && b > a iff a == b ? Potentially my implementation would break > this assumption when the relative IPs are the same, but the DSO is different. > > So is this what you want: > > +static enum match_result match_address_dso(struct dso *left_dso, u64 > left_ip, + struct dso *right_dso, u64 > right_ip) > +{ > + if (left_dso == right_dso && left_ip == right_ip) > + return MATCH_EQ; > + else if (left_dso < right_dso || left_ip < right_ip) > + return MATCH_LT; > + else > + return MATCH_GT; > +}
Why not do all in terms of absolute addresses? Comparing relative addresses seems nonsensical anyway. Perhaps something like the patch below, and note that cnode->ip and node->ip already already are absolute addresses.
Ravi?
- Arnaldo
diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c index 35a920f09503..1ac3f4a5afab 100644 --- a/tools/perf/util/callchain.c +++ b/tools/perf/util/callchain.c @@ -671,8 +671,6 @@ static enum match_result match_chain(struct callchain_cursor_node *node, { struct symbol *sym = node->sym; u64 left, right; - struct dso *left_dso = NULL; - struct dso *right_dso = NULL; if (callchain_param.key == CCKEY_SRCLINE) { enum match_result match = match_chain_strings(cnode->srcline, @@ -698,16 +696,14 @@ static enum match_result match_chain(struct callchain_cursor_node *node, return match_chain_strings(cnode->ms.sym->name, node->sym->name); - left = cnode->ms.sym->start; - right = sym->start; - left_dso = cnode->ms.map->dso; - right_dso = node->map->dso; + left = cnode->ms.map->unmap_ip(cnode->ms.map, cnode->ms.sym->start); + right = node->map->unmap_ip(node->map, sym->start); } else { left = cnode->ip; right = node->ip; } - if (left == right && left_dso == right_dso) { + if (left == right) { if (node->branch) { cnode->branch_count++;
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