Re: [PATCH net-next 2/2] net: avoid calling sched_clock when LLSis off

From: Andi Kleen
Date: Fri Jun 28 2013 - 10:39:03 EST


> diff --git a/fs/select.c b/fs/select.c
> index 79b876e..3654075 100644
> --- a/fs/select.c
> +++ b/fs/select.c
> @@ -402,7 +402,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
> poll_table *wait;
> int retval, i, timed_out = 0;
> unsigned long slack = 0;
> - unsigned int ll_flag = POLL_LL;
> + unsigned int ll_flag = ll_get_flag();

Is that a global flag? That's still the wrong level. It should
look at something in the file descriptor (preferably without
fetching any new cache lines)

-Andi

>
> +static inline unsigned int ll_get_flag(void)
> +{
> + return sysctl_net_ll_poll ? POLL_LL : 0;
> +}
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