From: Thomas Gleixner <tglx@linutronix.de>
To: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>,
shreyas@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
peterz@infradead.org, rafael@kernel.org,
vincent.guittot@linaro.org
Subject: Re: [PATCH V4] irq: Track the interrupt timings
Date: Tue, 14 Jun 2016 18:36:01 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.11.1606141833180.5839@nanos> (raw)
In-Reply-To: <alpine.LFD.2.20.1606141105320.1714@knanqh.ubzr>
On Tue, 14 Jun 2016, Nicolas Pitre wrote:
> On Tue, 14 Jun 2016, Daniel Lezcano wrote:
> > If the storage is a bit larger (let's say 16 values) and there is no memset
> > and the sum is not computed, at least we need a count for the number of values
> > in the array before this one is fulfilled, otherwise the statistics will be
> > wrong as we will take into account the entire array with old values, no ?
>
> The point is not to change from 8 to 16 entries, but to store raw 64-bit
> timestamps instead of computed 32-bit deltas. Whether or not those
> timestamps are too far apart and discarded can be done at idle entry
> time.
Correct, and you don't have to know how many timestamps are in the array
simply because if it is cleared at init time, then any not yet set value will
create a large gap, which you filter out.
The point is to make the fast path overhead as small as possible. And if
that's just a store and index increment, then it can be inline and not a
function call.
Thanks,
tglx
prev parent reply other threads:[~2016-06-14 16:38 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-13 11:05 [PATCH V4] irq: Track the interrupt timings Daniel Lezcano
2016-04-22 18:21 ` Daniel Lezcano
2016-05-03 13:44 ` Daniel Lezcano
2016-06-10 14:52 ` Thomas Gleixner
2016-06-10 15:11 ` Nicolas Pitre
2016-06-10 15:20 ` Thomas Gleixner
2016-06-10 15:29 ` Nicolas Pitre
2016-06-14 13:36 ` Daniel Lezcano
2016-06-14 15:10 ` Nicolas Pitre
2016-06-14 15:38 ` Daniel Lezcano
2016-06-14 16:36 ` Thomas Gleixner [this message]
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