From: Arun Sharma <asharma@fb.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: <linux-kernel@vger.kernel.org>, Kumar Sundararajan <kumar@fb.com>,
john stultz <johnstul@us.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Richard Cochran <richardcochran@gmail.com>
Subject: Re: [PATCH 1/4] Add clock_gettime_ns syscall
Date: Wed, 28 Dec 2011 11:02:03 -0800 [thread overview]
Message-ID: <4EFB67AB.7060707@fb.com> (raw)
In-Reply-To: <16ecaa6abb8b7a25ef31970f71a42c7e2ba5416c.1324831829.git.luto@amacapital.net>
On 12/25/11 8:51 AM, Andy Lutomirski wrote:
> +struct timens {
> + u64 ns; /* nanoseconds since the relevant epoch */
> + u64 padding; /* for future expansion (UTC offset? sub-ns?) */
> +};
>..
> +SYSCALL_DEFINE2(clock_gettime_ns, const clockid_t, which_clock,
> + struct timens __user *, tp)
> +{
How about returning a (signed) long as the time in ns? This way, we save
a store and a load and the value can be passed in registers.
This shouldn't preclude future expansion via extra args.
-Arun
next prev parent reply other threads:[~2011-12-28 19:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-25 16:50 [PATCH 0/4] clock_gettime_ns and x86-64 optimizations Andy Lutomirski
2011-12-25 16:51 ` [PATCH 1/4] Add clock_gettime_ns syscall Andy Lutomirski
2011-12-27 7:25 ` Richard Cochran
2011-12-28 19:02 ` Arun Sharma [this message]
[not found] ` <CALCETrVz1ADNxeLzPmeWXPU5ApfKURH2vnged2A2Vng8-hUxcw@mail.gmail.com>
2011-12-28 22:45 ` Arun Sharma
2011-12-28 23:42 ` Andy Lutomirski
2011-12-29 0:19 ` Arun Sharma
2011-12-25 16:51 ` [PATCH 2/4] x86-64: Add __vdso_clock_gettime_ns vsyscall Andy Lutomirski
2011-12-25 16:51 ` [PATCH 3/4] x86-64: Optimize vdso clock_gettime Andy Lutomirski
2011-12-25 16:51 ` [PATCH 4/4] x86-64: Inline vdso clock_gettime helpers Andy Lutomirski
2011-12-27 7:46 ` [PATCH 0/4] clock_gettime_ns and x86-64 optimizations Richard Cochran
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