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

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Date:   Wed, 2 Dec 2020 17:18:56 +0300
From:   Alexei Budankov <abudankov@...wei.com>
To:     "Bayduraev, Alexey V" <alexey.v.bayduraev@...ux.intel.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>, <abudankov@...wei.com>
Subject: Re: [PATCH v2 1/3] Revert "perf session: Fix decompression of
 PERF_RECORD_COMPRESSED records"


Hi Alexey. Please see below.

On 02.12.2020 17:04, Bayduraev, Alexey V wrote:
> 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.

Next time please avoid top posting and reply in line.
For this specific case it is right here just below my
previous answer.

Thanks,
Alexei