From 18ca42a51351dc83797628d8dca8bee1d64e6171 Mon Sep 17 00:00:00 2001
From: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Date: Thu, 30 Mar 2017 23:08:03 +0300
Subject: [PATCH 053/146] iwlwifi: mvm: avoid unnecessary cache trashing in Tx
path
Git-commit: 6f2f019495f637375b6d9dbbfa164b5b1e9d5583
Patch-mainline: v4.13-rc1
References: FATE#322675
When sending a Tx Command with a Tx packet, we allocate the
Tx command separately from the payload of the packet.
The WiFi MAC header is then copied into the buffer that was
allocated for the Tx Command. This means that this buffer
needs to be big enough to contain both. This is why it is
allocated with iwl_trans_alloc_tx_cmd which returns a
pointer to a newly allocated not zeroed struct
iwl_device_cmd.
The Tx command has a few bit fields and hence it needs to
be zeroed, but all the rest of the buffer doesn't need to
be zeroed since it will either be memcopy'ed with the MAC
header, or not even sent to the device.
This means that we don't need to zero all the
iwl_device_cmd structure, but rather only the size of
the iwl_tx_cmd structure.
Since sizeof(iwl_tx_cmd) - sizeof(iwl_tx_cmd) is about
260 bytes, this can avoid touching 4 cache lines for each
packet.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
drivers/net/wireless/intel/iwlwifi/mvm/tx.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/tx.c b/drivers/net/wireless/intel/iwlwifi/mvm/tx.c
index 5a87e4167cb1..bc4030b7da63 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/tx.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/tx.c
@@ -473,7 +473,10 @@ iwl_mvm_set_tx_params(struct iwl_mvm *mvm, struct sk_buff *skb,
if (unlikely(!dev_cmd))
return NULL;
- memset(dev_cmd, 0, sizeof(*dev_cmd));
+ /* Make sure we zero enough of dev_cmd */
+ BUILD_BUG_ON(sizeof(struct iwl_tx_cmd_gen2) > sizeof(*tx_cmd));
+
+ memset(dev_cmd, 0, sizeof(dev_cmd->hdr) + sizeof(*tx_cmd));
dev_cmd->hdr.cmd = TX_CMD;
if (iwl_mvm_has_new_tx_api(mvm)) {
--
2.12.3