netdev - Re: sha512: make it work, undo percpu message schedule

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Date:	Fri, 13 Jan 2012 11:41:41 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Alexey Dobriyan <adobriyan@...il.com>,
	linux-crypto@...r.kernel.org, netdev@...r.kernel.org,
	ken@...elabs.ch, Steffen Klassert <steffen.klassert@...unet.com>
Subject: Re: sha512: make it work, undo percpu message schedule

Le vendredi 13 janvier 2012 à 11:35 +0100, Eric Dumazet a écrit :

> I wonder ...
> 
> With 4096 cpus, do we really want to reserve 5242880 bytes of memory for
> this function ?
> 
> What about following patch instead ?
> 
> (Trying a dynamic memory allocation, and fallback on a single
> pre-allocated bloc of memory, shared by all cpus, protected by a
> spinlock)
> 
> diff --git a/crypto/sha512_generic.c b/crypto/sha512_generic.c
> index 9ed9f60..5c80a76 100644
> --- a/crypto/sha512_generic.c
> +++ b/crypto/sha512_generic.c
> @@ -21,7 +21,6 @@
>  #include <linux/percpu.h>
>  #include <asm/byteorder.h>
>  
> -static DEFINE_PER_CPU(u64[80], msg_schedule);
>  
>  static inline u64 Ch(u64 x, u64 y, u64 z)
>  {
> @@ -87,10 +86,16 @@ static void
>  sha512_transform(u64 *state, const u8 *input)
>  {
>  	u64 a, b, c, d, e, f, g, h, t1, t2;
> -
> +	static u64 msg_schedule[80];
> +	static DEFINE_SPINLOCK(msg_schedule_lock);
>  	int i;
> -	u64 *W = get_cpu_var(msg_schedule);
> +	u64 *W = kzalloc(sizeof(msg_schedule), GFP_ATOMIC | __GFP_NOWARN);
>  

And a plain kmalloc() is enough, since we fully initialize the array a
bit later.

	for (i = 0; i < 16; i++)
		LOAD_OP(i, W, input);
	for (i = 16; i < 80; i++) {
		BLEND_OP(i, W);
	}




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