From 8d1f7ecd2af55c0c82ffd2bff0ef0b26f16ea69f Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Sat, 23 Feb 2013 00:59:03 +0100 Subject: mac80211: defer tailroom counter manipulation when roaming During roaming, the crypto_tx_tailroom_needed_cnt counter will often take values 2,1,0,1,2 because first keys are removed and then new keys are added. This is inefficient because during the 0->1 transition, synchronize_net must be called to avoid packet races, although typically no packets would be flowing during that time. To avoid that, defer the decrement (2->1, 1->0) when keys are removed (by half a second). This means the counter will really have the values 2,2,2,3,4 ... 2, thus never reaching 0 and having to do the 0->1 transition. Note that this patch entirely disregards the drivers for which this optimisation was done to start with, for them the key removal itself will be expensive because it has to synchronize_net() after the counter is incremented to remove the key from HW crypto. For them the sequence will look like this: 0,1,0,1,0,1,0,1,0 (*) which is clearly a lot more inefficient. This could be addressed separately, during key removal the 0->1->0 sequence isn't necessary. (*) it starts at 0 because HW crypto is on, then goes to 1 when HW crypto is disabled for a key, then back to 0 because the key is deleted; this happens for both keys in the example. When new keys are added, it goes to 1 first because they're added in software; when a key is moved to hardware it goes back to 0 Signed-off-by: Johannes Berg --- net/mac80211/ieee80211_i.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'net/mac80211/ieee80211_i.h') diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h index 0acc07b852a9..54d09ec3fe68 100644 --- a/net/mac80211/ieee80211_i.h +++ b/net/mac80211/ieee80211_i.h @@ -680,6 +680,8 @@ struct ieee80211_sub_if_data { /* count for keys needing tailroom space allocation */ int crypto_tx_tailroom_needed_cnt; + int crypto_tx_tailroom_pending_dec; + struct delayed_work dec_tailroom_needed_wk; struct net_device *dev; struct ieee80211_local *local; -- cgit v1.2.2