Re: [PATCH v4 03/17] wlcore: Align reg_ch_conf_pending and tmp_ch_bitmap to unsigned long for better performance

Paolo Bonzini
2019-03-04T13:09:30Z

On 04/03/19 13:41, Peter Zijlstra wrote:
> On Mon, Mar 04, 2019 at 11:46:52AM +0100, Paolo Bonzini wrote:
>> From: Paolo Bonzini <pbonzini@redhat.com>
>> Subject: [PATCH] wlcore: simplify/fix/optimize reg_ch_conf_pending operations
>>
>> Bitmaps are defined on unsigned longs, so the usage of u32[2] in the
>> wlcore driver is incorrect. As noted by Peter Zijlstra, casting arrays
>> to a bitmap is incorrect for big-endian architectures.
>>
>> When looking at it I observed that:
>>
>> - operations on reg_ch_conf_pending is always under the wl_lock mutex,
>> so set_bit is overkill
>>
>> - the only case where reg_ch_conf_pending is accessed a u32 at a time is
>> unnecessary too.
>>
>> This patch cleans up everything in this area, and changes tmp_ch_bitmap
>> to have the proper alignment.
>>
>> Reported-by: Fenghua Yu <fenghua.yu@intel.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>
>> diff --git a/drivers/net/wireless/ti/wlcore/cmd.c b/drivers/net/wireless/ti/wlcore/cmd.c
>> index 903968735a74..3e093f3a7ec8 100644
>> --- a/drivers/net/wireless/ti/wlcore/cmd.c
>> +++ b/drivers/net/wireless/ti/wlcore/cmd.c
>> @@ -1700,14 +1700,14 @@ void wlcore_set_pending_regdomain_ch(struct wl1271 *wl, u16 channel,
>> ch_bit_idx = wlcore_get_reg_conf_ch_idx(band, channel);
>>
>> if (ch_bit_idx >= 0 && ch_bit_idx <= WL1271_MAX_CHANNELS)
>> - set_bit(ch_bit_idx, (long *)wl->reg_ch_conf_pending);
>> + __set_bit_le(ch_bit_idx, (long *)wl->reg_ch_conf_pending);
>> }
>>
>> int wlcore_cmd_regdomain_config_locked(struct wl1271 *wl)
>> {
>> struct wl12xx_cmd_regdomain_dfs_config *cmd = NULL;
>> int ret = 0, i, b, ch_bit_idx;
>> - u32 tmp_ch_bitmap[2];
>> + u32 tmp_ch_bitmap[2] __aligned(sizeof(unsigned long));
>
> Also mark it as __le32 ?

That would require more changes to mark ch_bit_map1/ch_bit_map2 as
__le32 (I think, I don't do much sparse), so I didn't do that.

>> struct wiphy *wiphy = wl->hw->wiphy;
>> struct ieee80211_supported_band *band;
>> bool timeout = false;
>> @@ -1717,7 +1717,7 @@ int wlcore_cmd_regdomain_config_locked(struct wl1271 *wl)
>>
>> wl1271_debug(DEBUG_CMD, "cmd reg domain config");
>>
>> - memset(tmp_ch_bitmap, 0, sizeof(tmp_ch_bitmap));
>> + memcpy(tmp_ch_bitmap, wl->reg_ch_conf_pending, sizeof(tmp_ch_bitmap));
>
> How about using:
>
> bitmap_to_arr32(tmp_ch_bitmap, wl->reg_ch_conf_pending, sizeof(tmp_ch_bitmap));
> for (i=0; i<2; i++)
> tmp_ch_bitmap[i] = cpu_to_le32(tmp_ch_bitmap[i]);
>
> (or add bitmap_to_arr32_le ?)

I've used __set_bit_le when setting reg_ch_conf_pending so no need to
swizzle here; OTOH bitmap_to_arr32 doesn't work here that swizzle
already swaps halfwords.

>> for (b = NL80211_BAND_2GHZ; b <= NL80211_BAND_5GHZ; b++) {
>> band = wiphy->bands[b];
>> @@ -1738,13 +1738,10 @@ int wlcore_cmd_regdomain_config_locked(struct wl1271 *wl)
>> if (ch_bit_idx < 0)
>> continue;
>>
>> - set_bit(ch_bit_idx, (long *)tmp_ch_bitmap);
>> + __set_bit_le(ch_bit_idx, (long *)tmp_ch_bitmap);
>
> But you copied in reg_ch_conf_pending without doing an LE swizzle.
> With the proposed change, we have two __le32 here and it works again.

(Again there's no need to do an LE swizzle because it's done in
wlcore_set_pending_regdomain_ch).

>> }
>> }
>>
>> - tmp_ch_bitmap[0] |= wl->reg_ch_conf_pending[0];
>> - tmp_ch_bitmap[1] |= wl->reg_ch_conf_pending[1];
>> -
>> if (!memcmp(tmp_ch_bitmap, wl->reg_ch_conf_last, sizeof(tmp_ch_bitmap)))
>> goto out;
>>
>
> And then remove the cpu_to_le32() on assignment to ch_bit_map*.

Yup, I forgot to commit that cpu_to_le32 removal.

>> diff --git a/drivers/net/wireless/ti/wlcore/wlcore.h b/drivers/net/wireless/ti/wlcore/wlcore.h
>> index dd14850b0603..870eea3e7a27 100644
>> --- a/drivers/net/wireless/ti/wlcore/wlcore.h
>> +++ b/drivers/net/wireless/ti/wlcore/wlcore.h
>> @@ -320,9 +320,9 @@ struct wl1271 {
>> bool watchdog_recovery;
>>
>> /* Reg domain last configuration */
>> - u32 reg_ch_conf_last[2] __aligned(8);
>> + DECLARE_BITMAP(reg_ch_conf_last, 64);
>
> Is never actually used as a bitmap but used as opaque storage with
> memcpy and memcmp against tmp_ch_bitmap.

Yeah, but it is the easiest way to ensure it is the right size as
reg_ch_conf_pending. The two are related, it makes sense to declare
them the same.

Paolo