2007-06-14 09:08:38

by Johannes Berg

Subject: [PATCH] conserve stack space due to padding

This patch reorders some fields in struct ieee802_11_elems to save 17*7
or 17*3 bytes (on 64/32-bit machines respectively) stack space in a few
functions.

Signed-off-by: Johannes Berg <[email protected]>

---
I don't think this hurts readability at all since these things are
*very* structured to begin with. And having 8/4 byte fields alternate
with 1 byte fields isn't such a great idea.

net/mac80211/ieee80211_sta.c | 35 +++++++++++++++++++----------------
1 file changed, 19 insertions(+), 16 deletions(-)

--- wireless-dev.orig/net/mac80211/ieee80211_sta.c 2007-06-14 09:19:48.780669913 +0200
+++ wireless-dev/net/mac80211/ieee80211_sta.c 2007-06-14 09:21:28.720669913 +0200
@@ -79,39 +79,42 @@ static int ieee80211_sta_config_auth(str

/* Parsed Information Elements */
struct ieee802_11_elems {
+ /* pointers to IEs */
u8 *ssid;
- u8 ssid_len;
u8 *supp_rates;
- u8 supp_rates_len;
u8 *fh_params;
- u8 fh_params_len;
u8 *ds_params;
- u8 ds_params_len;
u8 *cf_params;
- u8 cf_params_len;
u8 *tim;
- u8 tim_len;
u8 *ibss_params;
- u8 ibss_params_len;
u8 *challenge;
- u8 challenge_len;
u8 *wpa;
- u8 wpa_len;
u8 *rsn;
- u8 rsn_len;
u8 *erp_info;
- u8 erp_info_len;
u8 *ht_cap_param;
- u8 ht_cap_param_len;
u8 *ht_extra_param;
- u8 ht_extra_param_len;
u8 *ext_supp_rates;
- u8 ext_supp_rates_len;
u8 *wmm_info;
- u8 wmm_info_len;
u8 *wmm_param;
- u8 wmm_param_len;
u8 *tspec;
+
+ /* length of them, respectively */
+ u8 ssid_len;
+ u8 supp_rates_len;
+ u8 fh_params_len;
+ u8 ds_params_len;
+ u8 cf_params_len;
+ u8 tim_len;
+ u8 ibss_params_len;
+ u8 challenge_len;
+ u8 wpa_len;
+ u8 rsn_len;
+ u8 erp_info_len;
+ u8 ht_cap_param_len;
+ u8 ht_extra_param_len;
+ u8 ext_supp_rates_len;
+ u8 wmm_info_len;
+ u8 wmm_param_len;
u8 tspec_len;
};

2007-06-15 13:30:50

by Jiri Benc

Subject: Re: [PATCH] conserve stack space due to padding

On Thu, 14 Jun 2007 09:26:11 +0200, Johannes Berg wrote:
> This patch reorders some fields in struct ieee802_11_elems to save 17*7
> or 17*3 bytes (on 64/32-bit machines respectively) stack space in a few
> functions.
>
> Signed-off-by: Johannes Berg <[email protected]>

Acked-by: Jiri Benc <[email protected]>

--
Jiri Benc
SUSE Labs