From: Arnd Bergmann <arnd@arndb.de>
To: Tina Ruchandani <ruchandani.tina@gmail.com>
Cc: y2038@lists.linaro.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org, Wentao Xu <wentaox@codeaurora.org>,
Thierry Reding <treding@nvidia.com>, Hai Li <hali@codeaurora.org>
Subject: Re: [PATCH v2] drm/msm: Use 64-bit timekeeping
Date: Sun, 17 Apr 2016 01:47:24 +0200 [thread overview]
Message-ID: <4683452.tNFHTvCUEu@wuerfel> (raw)
In-Reply-To: <20160413095214.GA101605@localhost>
On Wednesday 13 April 2016 02:52:14 Tina Ruchandani wrote:
> ktime_t rem = ktime_sub(*timeout, now);
> - struct timespec ts = ktime_to_timespec(rem);
> - remaining_jiffies = timespec_to_jiffies(&ts);
> + struct timespec64 ts = ktime_to_timespec64(rem);
> +
> + remaining_jiffies = timespec64_to_jiffies(&ts);
>
Hi Tina,
The change looks correct to me, but I wonder if we should optimize
this code a little more, as it does two expensive 64-bit divisions.
How about
remaining_jiffies = msecs_to_jiffies(ktime_ms_delta(*timeout, now));
which only does one 64-bit division, and it's one that we can probably
optimize out in the future (we can check in ktime_ms_delta whether the
difference is more than 2^32 nanoseconds as the fast path).
Arnd
next prev parent reply other threads:[~2016-04-16 23:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-13 9:52 [PATCH v2] drm/msm: Use 64-bit timekeeping Tina Ruchandani
2016-04-16 23:47 ` Arnd Bergmann [this message]
2016-04-21 11:35 ` Tina Ruchandani
2016-04-21 11:39 ` Tina Ruchandani
2016-04-21 12:21 ` Arnd Bergmann
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