linux-kernel - Re: [PATCH v2 3/3] hw_random: increase schedule timeout in rng_dev

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Message-ID: <20140915181331.4e3f5fed@wiggum>
Date:	Mon, 15 Sep 2014 18:13:31 +0200
From:	Michael Büsch <m@...s.ch>
To:	Amos Kong <akong@...hat.com>
Cc:	virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
	herbert@...dor.apana.org.au, mpm@...enic.com,
	rusty@...tcorp.com.au, amit.shah@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] hw_random: increase schedule timeout in
 rng_dev_read()

On Tue, 16 Sep 2014 00:02:29 +0800
Amos Kong <akong@...hat.com> wrote:

> This patch increases the schedule timeout to 10 jiffies, it's more
> appropriate, then other takes can easy to hold the mutex lock.
> 
> Signed-off-by: Amos Kong <akong@...hat.com>
> ---
>  drivers/char/hw_random/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index 263a370..b5d1b6f 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -195,7 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
>  
>  		mutex_unlock(&rng_mutex);
>  
> -		schedule_timeout_interruptible(1);
> +		schedule_timeout_interruptible(10);
>  
>  		if (signal_pending(current)) {
>  			err = -ERESTARTSYS;

Does a schedule of 1 ms or 10 ms decrease the throughput?
I think we need some benchmarks.

-- 
Michael

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