linux-kernel - Re: [PATCH v2 1/3] Revert "perf session: Fix decompression of PERF_RECORD

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Date:   Wed, 2 Dec 2020 17:04:47 +0300
From:   "Bayduraev, Alexey V" <alexey.v.bayduraev@...ux.intel.com>
To:     Alexei Budankov <abudankov@...wei.com>,
        Jiri Olsa <jolsa@...hat.com>, Petr Malat <oss@...at.biz>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [PATCH v2 1/3] Revert "perf session: Fix decompression of
 PERF_RECORD_COMPRESSED records"

Hi,

I was able to reproduce "Couldn't allocate memory for decompression" on 32-bit 
perf with long perf.data.

On my side mmap() in perf_session__process_compressed_event() fails with ENOMEM,
due to exceeded memory limit for 32-bit applications.
This happens with or without Petr's patch.

As I can see, these mappings are only released in perf_session__delete().
We should think how to release them early.

On 02.12.2020 0:28, Alexei Budankov wrote:
> 
> Eventually sending to the proper Alexey's address.
> 
> On 02.12.2020 0:04, Alexei Budankov wrote:
>>
>> On 01.12.2020 22:09, Jiri Olsa wrote:
>>> On Mon, Nov 30, 2020 at 12:40:20PM +0100, Petr Malat wrote:
>>>> Hi Jiří,
>>>> were you able to reproduce the issue? I may also upload perf-archive
>>>> if that would help.
>>>
>>> oh yea ;-) seems like those 2 commits you reverted broke 32 bits
>>> perf for data files > 32MB
>>>
>>> but the fix you did does not work for Alexey's test he mentioned
>>> in the commit:
>>>
>>>       $ perf record -z -- some_long_running_workload
>>>       $ perf report --stdio -vv
>>>
>>> it's failing for me with:
>>>
>>> 	# ./perf report
>>> 	Couldn't allocate memory for decompression
>>> 	0xfe6f3a [0x60]: failed to process type: 81 [Operation not permitted]
>>> 	Error:
>>> 	failed to process sample
>>> 	# To display the perf.data header info, please use --header/--header-only options.
>>> 	#
>>>
>>> I think that's why here's special handling for compressed
>>> events, but I'll need to check on that in more detail,
>>> I was hoping for Alexey to answer ;-)
>>
>> Sorry for delay. Alexey Bayduraev could possibly help with that sooner.
>> Alexey, could you please follow up.
>>
>> Thanks,
>> Alexei

Regards,
Alexey