Re: [PATCH 3/7] [NET]: uninline dev_alloc_skb, de-bloats a lot

Denys Vlasenko
2008-03-27T23:38:57Z

On Thursday 27 March 2008 13:38, Ilpo Järvinen wrote:
> Allyesconfig (v2.6.24-mm1):
>
> -23668 392 funcs, 104 +, 23772 -, diff: -23668 --- dev_alloc_skb
>
> Without many debug CONFIGs (v2.6.25-rc2-mm1):
>
> -12178 382 funcs, 157 +, 12335 -, diff: -12178 --- dev_alloc_skb
> dev_alloc_skb | +37

This will be very confusing for casual reader:

> +struct sk_buff *dev_alloc_skb(unsigned int length)
> +{
> + return __dev_alloc_skb(length, GFP_ATOMIC);
> +}
> +EXPORT_SYMBOL(dev_alloc_skb);

"what, they want to save one push instruction per callsite??".

Can you add a comment which explains the intent?

+struct sk_buff *dev_alloc_skb(unsigned int length)
+{
+ /* There is more code here than it seems:
+ * __dev_alloc_skb is an inline */
+ return __dev_alloc_skb(length, GFP_ATOMIC);
+}
+EXPORT_SYMBOL(dev_alloc_skb);

Another good chunk of code size saving can be achieved
by introducing dev_alloc_skb_or_warn(), and using it
in places like these:

drivers/net/irda/nsc-ircc.c:

skb = dev_alloc_skb(len+1);
if (skb == NULL) {
IRDA_WARNING("%s(), memory squeeze, "
"dropping frame.\n",
__FUNCTION__);

drivers/net/appletalk/ltpc.c:

skb = dev_alloc_skb(3+sklen);
if (skb == NULL)
{
printk("%s: dropping packet due to memory squeeze.\n",

net/econet/af_econet.c:

newskb = alloc_skb((len - sizeof(struct aunhdr) + 15) & ~15,
GFP_ATOMIC);
if (newskb == NULL)
{
printk(KERN_DEBUG "AUN: memory squeeze, dropping packet.\n");
/* Send nack and hope sender tries again */
goto bad;
}

(hmm, this last one also wants s/alloc_skb(GFP_ATOMIC)/dev_alloc_skb/)

--
vda