Re: [PATCH v2 1/3] Revert "perf session: Fix decompression of PERF_RECORD_COMPRESSED records"

From: Alexei Budankov <abudankov@huawei.com>
To: "Bayduraev, Alexey V" <alexey.v.bayduraev@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Petr Malat <oss@malat.biz>
Cc: <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Kan Liang <kan.liang@linux.intel.com>, <abudankov@huawei.com>
Subject: Re: [PATCH v2 1/3] Revert "perf session: Fix decompression of PERF_RECORD_COMPRESSED records"
Date: Wed, 2 Dec 2020 17:18:56 +0300	[thread overview]
Message-ID: <53805573-fa3e-21af-4df8-82a5b8cc7beb@huawei.com> (raw)
In-Reply-To: <545dfd5b-670a-a215-4484-29fe10b18517@linux.intel.com>

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