iwlwifi: use paged Rx
This switches the iwlwifi driver to use paged skb from linear skb for Rx buffer. So that it relieves some Rx buffer allocation pressure for the memory subsystem. Currently iwlwifi (4K for 3945) requests 8K bytes for Rx buffer. Due to the trailing skb_shared_info in the skb->data, alloc_skb() will do the next order allocation, which is 16K bytes. This is suboptimal and more likely to fail when the system is under memory usage pressure. Switching to paged Rx skb lets us allocate the RXB directly by alloc_pages(), so that only order 1 allocation is required. It also adjusts the area spin_lock (with IRQ disabled) protected in the tasklet because tasklet guarentees to run only on one CPU and the new unprotected code can be preempted by the IRQ handler. This saves us from spawning another workqueue to make skb_linearize/__pskb_pull_tail happy (which cannot be called in hard irq context). Finally, mac80211 doesn't support paged Rx yet. So we linearize the skb for all the management frames and software decryption or defragmentation required data frames before handed to mac80211. For all the other frames, we __pskb_pull_tail 64 bytes in the linear area of the skb for mac80211 to handle them properly. Signed-off-by: Zhu Yi <yi.zhu@intel.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
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