From: Mel Gorman <mgorman@techsingularity.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, jolsa@redhat.com
Subject: Re: [PATCH v0 1/2] perf: Add an option to ask for high order allocations for AUX buffers
Date: Wed, 13 Feb 2019 19:17:06 +0000 [thread overview]
Message-ID: <20190213191705.GV9565@techsingularity.net> (raw)
In-Reply-To: <20190213175434.GA32494@hirez.programming.kicks-ass.net>
On Wed, Feb 13, 2019 at 06:54:34PM +0100, Peter Zijlstra wrote:
> On Wed, Feb 13, 2019 at 05:47:56PM +0000, Mel Gorman wrote:
> > If there is a tangiable performance benefit from using contiguous regions
> > then I would suggest optimistically allocating them with appropriate
> > GFP flags to avoid large latencies at startup time and fall back if
> > necessary.
>
> Right; the code does the fallback thing. It successively tries smaller
> order allocations until 0-order fails.
>
> It currently uses:
>
> #define PERF_AUX_GFP (GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_NORETRY)
>
> Is that what you could consider appropriate?
Yeah, spot on. Conceivably the semantics of __GFP_NORETY will change a
little at some point in the next year but not in any way I'd consider
harmful (depends on how THP and locality discussions go). Even *if*
we did something harmful, there will be complaints before it's problematic.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2019-02-13 19:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-13 11:47 [PATCH v0 0/2] perf: Allow forcing high-order allocation for AUX buffers Alexander Shishkin
2019-02-13 11:47 ` [PATCH v0 1/2] perf: Add an option to ask for high order allocations " Alexander Shishkin
2019-02-13 13:07 ` Peter Zijlstra
2019-02-13 13:49 ` Alexander Shishkin
2019-02-13 17:47 ` Mel Gorman
2019-02-13 17:54 ` Peter Zijlstra
2019-02-13 19:17 ` Mel Gorman [this message]
2019-02-13 11:47 ` [PATCH v0 2/2] perf record: Add --aux-highorder Alexander Shishkin
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