From: Leo Yan <leo.yan@linaro.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>,
Andi Kleen <ak@linux.intel.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 2/2] perf auxtrace: Optimize barriers with load-acquire and store-release
Date: Mon, 31 May 2021 23:10:49 +0800 [thread overview]
Message-ID: <20210531151049.GE9324@leoy-ThinkPad-X240s> (raw)
In-Reply-To: <20210519140319.1673043-2-leo.yan@linaro.org>
Hi Peter, Adrian,
On Wed, May 19, 2021 at 10:03:19PM +0800, Leo Yan wrote:
> Load-acquire and store-release are one-way permeable barriers, which can
> be used to guarantee the memory ordering between accessing the buffer
> data and the buffer's head / tail.
>
> This patch optimizes the memory ordering with the load-acquire and
> store-release barriers.
Is this patch okay for you?
Besides this patch, I have an extra question. You could see for
accessing the AUX buffer's head and tail, it also support to use
compiler build-in functions for atomicity accessing:
__sync_val_compare_and_swap()
__sync_bool_compare_and_swap()
Since now we have READ_ONCE()/WRITE_ONCE(), do you think we still need
to support __sync_xxx_compare_and_swap() atomicity?
I checked the code for updating head and tail for the perf ring buffer
(see ring_buffer_read_head() and ring_buffer_write_tail() in the file
tools/include/linux/ring_buffer.h), which doesn't support
__sync_xxx_compare_and_swap() anymore. This is why I wander if should
drop __sync_xxx_compare_and_swap() atomicity for AUX ring buffer as
well.
Thanks,
Leo
next prev parent reply other threads:[~2021-05-31 17:07 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-19 14:03 [PATCH v1 1/2] perf auxtrace: Change to use SMP memory barriers Leo Yan
2021-05-19 14:03 ` [PATCH v1 2/2] perf auxtrace: Optimize barriers with load-acquire and store-release Leo Yan
2021-05-31 15:10 ` Leo Yan [this message]
2021-05-31 15:55 ` Peter Zijlstra
2021-05-31 19:03 ` Adrian Hunter
2021-06-01 6:33 ` Leo Yan
2021-06-01 6:58 ` Peter Zijlstra
2021-06-01 9:07 ` Adrian Hunter
2021-06-01 9:17 ` Peter Zijlstra
2021-06-01 9:45 ` Adrian Hunter
2021-06-01 9:48 ` Peter Zijlstra
2021-06-01 14:56 ` Leo Yan
2021-06-01 6:48 ` Peter Zijlstra
2021-05-27 7:54 ` [PATCH v1 1/2] perf auxtrace: Change to use SMP memory barriers Adrian Hunter
2021-05-27 8:11 ` Peter Zijlstra
2021-05-27 8:25 ` Adrian Hunter
2021-05-27 9:24 ` Adrian Hunter
2021-05-27 9:57 ` Peter Zijlstra
2021-05-31 14:53 ` Leo Yan
2021-05-31 15:48 ` Peter Zijlstra
2021-06-01 3:21 ` Leo Yan
2021-05-27 9:45 ` Peter Zijlstra
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