On Fri, 2015-08-28 at 15:29 -0700, Eric Dumazet wrote: > On Fri, 2015-08-28 at 14:26 -0700, Joe Perches wrote: > 1) u64 array[XX] on stack is naturally aligned,
Of course it is. > kzalloc() wont improve this at all. Not sure what you believe. An alloc would only reduce stack use. Copying into the buffer, then copying the buffer into the skb may be desirable on some arches though. > 2) put_unaligned() is basically a normal memory write on x86. > memcpy(dst,src,...) will have a problem anyway on arches that care, > because src & dst wont have same alignment. OK, so all the world's an x86? On arm32, copying 288 bytes using nearly all aligned word transfers is generally faster than using only unsigned short transfers. > 288 bytes on stack in a leaf function in this path is totally fine, it > is not like we're calling ext4/xfs/nfs code after this point. Generally true. It's always difficult to know how much stack has been consumed though and smaller stack frames are generally better. Anyway, the block copy from either the alloc'd or stack buffer amounts only to a slight performance improvement for arm32. It doesn't really have much other utility. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
