On 5/18/07, Eric Dumazet <[EMAIL PROTECTED]> wrote:
On Fri, 18 May 2007 17:10:02 +0530 "pradeep singh" <[EMAIL PROTECTED]> wrote:> Hi , > > following code snippet is self evident in what it does - > > truct net_device *alloc_netdev(int sizeof_priv, const char *name, > void (*setup)(struct net_device *)) > { > void *p; > struct net_device *dev; > int alloc_size; > > /* ensure 32-byte alignment of both the device and private area */ > alloc_size = (sizeof(*dev) + NETDEV_ALIGN_CONST) & ~NETDEV_ALIGN_CONST; > alloc_size += sizeof_priv + NETDEV_ALIGN_CONST; > > p = kzalloc(alloc_size, GFP_KERNEL); > if (!p) { > printk(KERN_ERR "alloc_dev: Unable to allocate device.\n"); > return NULL; > } > [snip] > > Is the comment correct? yes it seems correct > Why is it 'ensure 32 byte alignment', instead of 32 bit alignment? Its 32 bytes, not bits. #define NETDEV_ALIGN 32 #define NETDEV_ALIGN_CONST (NETDEV_ALIGN - 1) > > What am i missing here? I dont know :) This 32 bytes alignement maybe not up2date, because net_device contains several ____cacheline_aligned_in_smp
Thanks eric got it. --psr
Would be nice to switch the alignement to max(L1_CACHE_SIZE, 32) nowadays, at least on SMP
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