From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, jolsa@redhat.com
Subject: Re: [PATCH v1 1/1] perf: Optimistically use high order allocations for AUX buffers
Date: Fri, 22 Feb 2019 14:57:05 +0200 [thread overview]
Message-ID: <87a7ioc76m.fsf@ashishki-desk.ger.corp.intel.com> (raw)
In-Reply-To: <20190215114727.62648-2-alexander.shishkin@linux.intel.com>
Alexander Shishkin <alexander.shishkin@linux.intel.com> writes:
> Currently, the AUX buffer allocator will use high-order allocations
> for PMUs that don't support hardware scatter-gather chaining to ensure
> large contiguous blocks of pages, and always use an array of single
> pages otherwise.
>
> There is, however, a tangible performance benefit in using larger chunks
> of contiguous memory even in the latter case, that comes from not having
> to fetch the next page's address at every page boundary. In particular,
> a task running under Intel PT on an Atom CPU shows 1.5%-2% less runtime
> penalty with a single multi-page output region in snapshot mode (no PMI)
> than with multiple single-page output regions, from ~6% down to ~4%. For
> the snapshot mode it does make a difference as it is intended to run over
> long periods of time.
>
> For this reason, change the allocation policy to always optimistically
> start with the highest possible order when allocating pages for the AUX
> buffer, desceding until the allocation succeeds or order zero allocation
> fails.
>
> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Does anybody want to pick this up?
Thanks,
--
Alex
next prev parent reply other threads:[~2019-02-22 12:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-15 11:47 [PATCH v1 0/1] perf: High-order AUX allocations Alexander Shishkin
2019-02-15 11:47 ` [PATCH v1 1/1] perf: Optimistically use high order allocations for AUX buffers Alexander Shishkin
2019-02-22 12:57 ` Alexander Shishkin [this message]
2019-03-09 14:38 ` [tip:perf/urgent] perf/ring_buffer: Use high order allocations for AUX buffers optimistically tip-bot for Alexander Shishkin
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