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From: Song Liu <songliubraving@fb.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Andi Kleen <ak@linux.intel.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>
Subject: Re: [PATCH 11/12] perf tools: Reuse shared eBPF dso objects
Date: Wed, 17 Apr 2019 16:56:41 +0000
Message-ID: <4CBDB645-513F-4CCA-9FA0-B29110F10C0E@fb.com> (raw)
In-Reply-To: <20190417073241.GC17024@krava>



> On Apr 17, 2019, at 12:32 AM, Jiri Olsa <jolsa@redhat.com> wrote:
> 
> On Wed, Apr 17, 2019 at 09:55:25AM +0300, Adrian Hunter wrote:
>> On 17/04/19 9:51 AM, Jiri Olsa wrote:
>>> On Wed, Apr 17, 2019 at 09:35:32AM +0300, Adrian Hunter wrote:
>>>> On 16/04/19 7:01 PM, Jiri Olsa wrote:
>>>>> The eBPF program can be loaded multiple times
>>>>> with the same name (tag). We can share dso
>>>>> objects for those programs.
>>>> 
>>>> Doesn't a eBPF program get recompiled differently every time it is loaded?
>>> 
>>> yes, but those with same tag are identical
>> 
>> But won't recompiled eBPF programs be different due to blinded constants?
>> Or perhaps in the future other code randomization?
> 
> ah right.. that can happen, let's skip this one then
> 
> perhaps we could add bpf prog id to be part of the name
> to make it unique.. I'll check
> 
> thanks,
> jirka

I thought about similar optimizations. However, this is not easy. 

Tag of a BPF program is calculated _before_ JiT, so we really cannot
say two programs with same tag are identical. Current implementation 
iterates over all bpf program IDs, so same program id will not appear
twice in the same perf session. 

I think the more realistic opportunity of optimizations comes from 
sharing the dsos cross multiple perf.data files. 

Thanks,
Song

>> 
>>> 
>>> jirka
>>> 
>>>> 
>>>>> 
>>>>> Link: http://lkml.kernel.org/n/tip-3damf8vq1dryhtpbk5b06jpt@git.kernel.org
>>>>> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
>>>>> ---
>>>>> tools/perf/util/machine.c | 14 +++++++++++---
>>>>> 1 file changed, 11 insertions(+), 3 deletions(-)
>>>>> 
>>>>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>>>>> index d4aa44489011..a60653827891 100644
>>>>> --- a/tools/perf/util/machine.c
>>>>> +++ b/tools/perf/util/machine.c
>>>>> @@ -23,6 +23,7 @@
>>>>> #include "linux/hash.h"
>>>>> #include "asm/bug.h"
>>>>> #include "bpf-event.h"
>>>>> +#include "dso.h"
>>>>> 
>>>>> #include "sane_ctype.h"
>>>>> #include <symbol/kallsyms.h>
>>>>> @@ -699,11 +700,18 @@ static int machine__process_ksymbol_register(struct machine *machine,
>>>>> 
>>>>> 	map = map_groups__find(&machine->kmaps, event->ksymbol_event.addr);
>>>>> 	if (!map) {
>>>>> -		map = dso__new_map(event->ksymbol_event.name);
>>>>> -		if (!map)
>>>>> +		struct dso *dso;
>>>>> +
>>>>> +		dso = dsos__findnew(&machine->dsos, event->ksymbol_event.name);
>>>>> +		if (!dso)
>>>>> 			return -ENOMEM;
>>>>> 
>>>>> -		map->start = event->ksymbol_event.addr;
>>>>> +		map = map__new2(event->ksymbol_event.addr, dso);
>>>>> +		if (!map) {
>>>>> +			dso__put(dso);
>>>>> +			return -ENOMEM;
>>>>> +		}
>>>>> +
>>>>> 		map->end = map->start + event->ksymbol_event.len;
>>>>> 		map_groups__insert(&machine->kmaps, map);
>>>>> 	}


  reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-16 16:01 [PATCH 00/12] perf tools: Display eBPF code in intel_pt trace Jiri Olsa
2019-04-16 16:01 ` [PATCH 01/12] perf tools: Separate generic code in dso__data_file_size Jiri Olsa
2019-04-16 16:01 ` [PATCH 02/12] perf tools: Separate generic code in dso_cache__read Jiri Olsa
2019-04-16 17:17   ` Stanislav Fomichev
2019-04-16 18:21     ` Jiri Olsa
2019-04-16 16:01 ` [PATCH 03/12] perf tools: Simplify dso_cache__read function Jiri Olsa
2019-04-16 16:01 ` [PATCH 04/12] perf tools: Add bpf dso read and size hooks Jiri Olsa
2019-04-16 16:01 ` [PATCH 05/12] perf tools: Read also the end of the kernel Jiri Olsa
2019-04-16 16:01 ` [PATCH 06/12] perf tools: Do not erase uncovered maps by kcore Jiri Olsa
2019-04-16 16:01 ` [PATCH 07/12] perf tools: Check maps for bpf programs Jiri Olsa
2019-04-16 19:31   ` Arnaldo Carvalho de Melo
2019-04-19 17:18   ` [tip:perf/urgent] " tip-bot for Song Liu
2019-04-16 16:01 ` [PATCH 08/12] perf tools: Fix side band thread draining Jiri Olsa
2019-04-16 19:33   ` Arnaldo Carvalho de Melo
2019-04-16 20:41   ` Song Liu
2019-04-19 17:19   ` [tip:perf/urgent] perf evlist: " tip-bot for Jiri Olsa
2019-04-16 16:01 ` [PATCH 09/12] perf tools: Fix map reference counting Jiri Olsa
2019-04-16 19:36   ` Arnaldo Carvalho de Melo
2019-04-19 17:20   ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2019-04-16 16:01 ` [PATCH 10/12] perf tools: Keep zero in pgoff bpf map Jiri Olsa
2019-04-16 16:01 ` [PATCH 11/12] perf tools: Reuse shared eBPF dso objects Jiri Olsa
2019-04-17  6:35   ` Adrian Hunter
2019-04-17  6:51     ` Jiri Olsa
2019-04-17  6:55       ` Adrian Hunter
2019-04-17  7:32         ` Jiri Olsa
2019-04-17 16:56           ` Song Liu [this message]
2019-04-16 16:01 ` [PATCH 12/12] perf script: Pad dso name for --call-trace Jiri Olsa

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