linux-kernel - Re: [RFC][PATCH 6/6] x86_64: GENERIC

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Date:	Wed, 9 Aug 2006 04:45:16 +0200
From:	Andi Kleen <ak@...e.de>
To:	john stultz <johnstul@...ibm.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 6/6] x86_64: GENERIC_TIME based vsyscall code

On Wednesday 09 August 2006 04:17, john stultz wrote:

> +	cycle_t ret;
> +	rdtscll(ret);


_sync


> +static cycle_t __vsyscall_fn vread_hpet(void)
> +{
> +	return (cycle_t)readl((void *)fix_to_virt(VSYSCALL_HPET) + 0xf0);
> +}

64bit HPET?


> +extern struct vsyscall_gtod_data_t vsyscall_gtod_data;

No extern in .c please
  

> +static __always_inline int syscall_gtod(struct timeval *tv, struct timezone *tz)
> +{
> +	int ret;
> +
> +	asm volatile("syscall"

You eliminated the patching away of the syscall opcode? Please retain that.



> -	tv->tv_sec = sec + usec / 1000000;
> -	tv->tv_usec = usec % 1000000;
> +		now = __vsyscall_gtod_data.clock.vread();
> +
> +		base = __vsyscall_gtod_data.clock.cycle_last;
> +		mask = __vsyscall_gtod_data.clock.mask;
> +		mult = __vsyscall_gtod_data.clock.mult;
> +		shift = __vsyscall_gtod_data.clock.shift;
> +
> +		*tv = __vsyscall_gtod_data.wall_time_tv;
> +
> +	} while (read_seqretry(&__vsyscall_gtod_data.lock, seq));

Do you have benchmarks on performance compared to the old code?

-Andi
-
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