From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: Andi Kleen <ak@linux.intel.com>, peterz@infradead.org
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, Jiri Olsa <jolsa@kernel.org>,
alexey.budankov@linux.intel.com, adrian.hunter@intel.com,
alexander.shishkin@linux.intel.com
Subject: Re: [PATCH 1/2] perf: Add closing sibling events' file descriptors
Date: Mon, 10 Aug 2020 16:57:55 +0300 [thread overview]
Message-ID: <875z9q1u3g.fsf@ashishki-desk.ger.corp.intel.com> (raw)
In-Reply-To: <20200806153205.GA1448395@tassilo.jf.intel.com>
Andi Kleen <ak@linux.intel.com> writes:
>> > This adds an opt-in flag to the perf_event_open() syscall to retain
>> > sibling events after their file descriptors are closed. In this case, the
>> > actual events will be closed with the group leader.
>>
>> So having the 1:1 relation with filedesc imposes a resource limit on
>> userspace.
>>
>> This patch breaks that and enables a user to basically DoS the system by
>> creating unbound events.
>
> The idea was to account the events in the locked memory allocation too.
> Not sure that made it into the patch though.
It didn't. I can't figure out what to charge on the locked memory, as
all that memory is in kernel-side objects. It also needs to make sense
as iirc the default MLOCK_LIMIT is quite low, you'd hit it sooner than
the file descriptor limit.
> It has a minor issue that it might break some existing setups that rely
> on the mmap fitting exactly into the mmap allocation, but that could
> be solved by allowing a little slack, since the existing setups
> likely don't have that many events.
I don't see how to make this work in a sane way. Besides, if we have to
have a limit anyway, sticking with the existing one is just easier and
1:1 is kind of more logical.
Regards,
--
Alex
next prev parent reply other threads:[~2020-08-10 13:58 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-08 15:16 [PATCH 0/2] perf: Allow closing siblings' file descriptors Alexander Shishkin
2020-07-08 15:16 ` [PATCH 1/2] perf: Add closing sibling events' " Alexander Shishkin
2020-08-06 8:35 ` peterz
2020-08-06 15:32 ` Andi Kleen
2020-08-10 13:57 ` Alexander Shishkin [this message]
2020-08-10 14:45 ` Andi Kleen
2020-08-10 20:36 ` Peter Zijlstra
2020-08-11 8:12 ` Alexey Budankov
2020-08-11 14:29 ` Andi Kleen
2020-08-11 14:47 ` David Laight
2020-08-11 18:03 ` Andi Kleen
2020-08-11 21:06 ` David Laight
2020-08-11 9:47 ` Alexander Shishkin
2020-08-11 14:34 ` Andi Kleen
2020-08-11 16:21 ` Alexander Shishkin
2020-08-11 18:02 ` Andi Kleen
2020-07-08 15:16 ` [PATCH 2/2] perf record: Support closing siblings' " Alexander Shishkin
2020-07-08 21:09 ` Jiri Olsa
2020-07-16 8:42 ` [perf record] d65f0cbbc6: perf-sanity-tests.Setup_struct_perf_event_attr.fail kernel test robot
2020-07-09 8:30 ` [PATCH 0/2] perf: Allow closing siblings' file descriptors Alexey Budankov
2020-08-06 6:15 ` Adrian Hunter
2020-08-06 8:37 ` peterz
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