Re: [RFC PATCH 2/2] mac80211: aes_ccm: cache AEAD request structures per CPU

On Tue, 2016-10-18 at 15:08 +0100, Ard Biesheuvel wrote:

+	aead_req = *this_cpu_ptr(ccmp->reqs);
+	if (!aead_req) {
+		aead_req = kzalloc(reqsize + CCM_AAD_LEN, GFP_ATOMIC);
+		if (!aead_req)
+			return -ENOMEM;
+		*this_cpu_ptr(ccmp->reqs) = aead_req;
+		aead_request_set_tfm(aead_req, ccmp->tfm);
+	}

Hmm. Is it really worth having a per-CPU variable for each possible
key? You could have a large number of those (typically three when
you're a client on an AP, and 1 + 1 for each client when you're the
AP).

Would it be so bad to have to set the TFM every time (if that's even
possible), and just have a single per-CPU cache?

johannes