iwlwifi: disable 8K A-MSDU by default

Supporting 8K A-MSDU means that we need to allocate order 1
pages for every Rx packet. Even when there is no traffic.
This adds stress on the memory manager. The handling of
compound pages is also less trivial for the memory manager
and not using them will make the allocation code run faster
although I didn't really measure.
Eric also pointed out that having huge buffers with little
data in them is not very nice towards the TCP stack since
the truesize of the skb is huge. This doesn't allow TCP
to have a big Rx window.
See https://patchwork.kernel.org/patch/2167711/ for details.

Note that very few vendors will actually send A-MSDU.
Disable this feature by default.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/drivers/net/wireless/iwlwifi/iwl-drv.c b/drivers/net/wireless/iwlwifi/iwl-drv.c
index 6f228bb2b84431e61cd8292d1563f81faa91efc6..fbfd2d1371176e247a22e5fca00ee5809088c306 100644 (file)
--- a/drivers/net/wireless/iwlwifi/iwl-drv.c
+++ b/drivers/net/wireless/iwlwifi/iwl-drv.c
@@ -1102,7 +1102,6 @@ void iwl_drv_stop(struct iwl_drv *drv)
 
 /* shared module parameters */
 struct iwl_mod_params iwlwifi_mod_params = {
-       .amsdu_size_8K = 1,
        .restart_fw = 1,
        .plcp_check = true,
        .bt_coex_active = true,
@@ -1207,7 +1206,7 @@ MODULE_PARM_DESC(11n_disable,
        "disable 11n functionality, bitmap: 1: full, 2: agg TX, 4: agg RX");
 module_param_named(amsdu_size_8K, iwlwifi_mod_params.amsdu_size_8K,
                   int, S_IRUGO);
-MODULE_PARM_DESC(amsdu_size_8K, "enable 8K amsdu size");
+MODULE_PARM_DESC(amsdu_size_8K, "enable 8K amsdu size (default 0)");
 module_param_named(fw_restart, iwlwifi_mod_params.restart_fw, int, S_IRUGO);
 MODULE_PARM_DESC(fw_restart, "restart firmware in case of error");
 

diff --git a/drivers/net/wireless/iwlwifi/iwl-modparams.h b/drivers/net/wireless/iwlwifi/iwl-modparams.h
index e5e3a79eae2fbd5e8f544db2cc9605522770dddb..2c2a729092f5e894013c39f1eccb0a739a5e56d4 100644 (file)
--- a/drivers/net/wireless/iwlwifi/iwl-modparams.h
+++ b/drivers/net/wireless/iwlwifi/iwl-modparams.h
@@ -91,7 +91,7 @@ enum iwl_power_level {
  * @sw_crypto: using hardware encryption, default = 0
  * @disable_11n: disable 11n capabilities, default = 0,
  *     use IWL_DISABLE_HT_* constants
- * @amsdu_size_8K: enable 8K amsdu size, default = 1
+ * @amsdu_size_8K: enable 8K amsdu size, default = 0
  * @restart_fw: restart firmware, default = 1
  * @plcp_check: enable plcp health check, default = true
  * @wd_disable: enable stuck queue check, default = 0