linux-kernel - [PATCH 0/2] perf: Fix AUX software double buffering

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Message-Id: <20190503085536.24119-1-alexander.shishkin@linux.intel.com>
Date:   Fri,  3 May 2019 11:55:34 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        jolsa@...hat.com, adrian.hunter@...el.com,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH 0/2] perf: Fix AUX software double buffering

Hi Peter,

There was a problem with 04fe30a61514 ("perf/ring_buffer: Use high order
allocations for AUX buffers optimistically") that made buffers that were
previously scattered across multiple pages into one large buffer, breaking
double buffering. In practice, this manifests easily for non-privileged
users, whose buffers are generally smaller than MAX_ORDER and would fit
into one high-order allocation. Root's default AUX buffer size is larger
and would get split, so they are less affected. The fix is trivial and
we also get rid of one PMU capability as a bonus.

Alexander Shishkin (2):
  perf: Fix AUX software double buffering
  perf, pt: Remove software double buffering PMU capability

 arch/x86/events/intel/pt.c  | 3 +--
 include/linux/perf_event.h  | 1 -
 kernel/events/ring_buffer.c | 3 +--
 3 files changed, 2 insertions(+), 5 deletions(-)

-- 
2.20.1