From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6B2CC43381 for ; Mon, 4 Mar 2019 14:47:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9ED1020815 for ; Mon, 4 Mar 2019 14:47:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726949AbfCDOrq (ORCPT ); Mon, 4 Mar 2019 09:47:46 -0500 Received: from mga01.intel.com ([192.55.52.88]:32215 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726261AbfCDOrq (ORCPT ); Mon, 4 Mar 2019 09:47:46 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Mar 2019 06:47:45 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,440,1544515200"; d="scan'208";a="304248956" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by orsmga005.jf.intel.com with ESMTP; 04 Mar 2019 06:47:44 -0800 Date: Mon, 4 Mar 2019 06:40:50 -0800 From: Fenghua Yu To: Paolo Bonzini Cc: Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Dave Hansen , Ashok Raj , Ravi V Shankar , Xiaoyao Li , linux-kernel , x86 , kvm@vger.kernel.org Subject: Re: [PATCH v4 03/17] wlcore: Align reg_ch_conf_pending and tmp_ch_bitmap to unsigned long for better performance Message-ID: <20190304144050.GA230561@romley-ivt3.sc.intel.com> References: <1551494711-213533-1-git-send-email-fenghua.yu@intel.com> <1551494711-213533-4-git-send-email-fenghua.yu@intel.com> <20190304101141.GB32477@hirez.programming.kicks-ass.net> <44bb6771-7aea-c44d-6605-45e7a1499d1b@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <44bb6771-7aea-c44d-6605-45e7a1499d1b@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 04, 2019 at 11:46:52AM +0100, Paolo Bonzini wrote: > On 04/03/19 11:11, Peter Zijlstra wrote: > > On Fri, Mar 01, 2019 at 06:44:57PM -0800, Fenghua Yu wrote: > >> A bit in reg_ch_conf_pending in wl271 and tmp_ch_bitmap is set > >> atomically by set_bit(). set_bit() sets the bit in a single > >> unsigned long location. If the variables are not aligned to > >> unsigned long, set_bit() accesses two cache lines and thus causes > >> slower performance. On x86, this scenario is called split lock and > >> can cause overall performance degradation due to locked BTSL > >> instruction in set_bit() locks bus. > >> > >> To avoid performance degradation, the two variables are aligned to > >> unsigned long. > >> > >> Signed-off-by: Fenghua Yu --- > >> drivers/net/wireless/ti/wlcore/cmd.c | 3 ++- > >> drivers/net/wireless/ti/wlcore/wlcore.h | 6 ++++-- 2 files > >> changed, 6 insertions(+), 3 deletions(-) > >> > >> diff --git a/drivers/net/wireless/ti/wlcore/cmd.c > >> b/drivers/net/wireless/ti/wlcore/cmd.c index > >> 903968735a74..8d15a6307d44 100644 --- > >> a/drivers/net/wireless/ti/wlcore/cmd.c +++ > >> b/drivers/net/wireless/ti/wlcore/cmd.c @@ -1707,7 +1707,8 @@ 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]; + /* Align to unsigned long > >> for better performance in set_bit() */ + u32 tmp_ch_bitmap[2] > >> __aligned(sizeof(unsigned long)); > > This is the only place where an array of u32 is needed, because of > > cmd->ch_bit_map1 = cpu_to_le32(tmp_ch_bitmap[0]); > cmd->ch_bit_map2 = cpu_to_le32(tmp_ch_bitmap[1]); > > All the others should use DECLARE_BITMAP, including reg_ch_conf_last > which was already using __aligned. As Peter mentioned they should > also use set_bit_le. Actually they do not need locked access at all > because the only code paths to the set_bit take a mutex. > > There is one other place that is accessing the items of the array, but > it is fixed easily. The following patch should do everything: > > ------------------- 8< -------------------------- > From: Paolo Bonzini > 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 > Signed-off-by: Paolo Bonzini > > 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)); Now __aligned() is unnecessary because __set_bit_le() handles tmp_ch_bitmap, right? > 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)); > > 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); Is __test_and_set_bit_le() more meaningful to avoid duplicate bit setting ? > } > } > > - 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; > > 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); > /* Reg domain pending configuration */ > - u32 reg_ch_conf_pending[2]; > + DECLARE_BITMAP(reg_ch_conf_pending, 64); > > /* Pointer that holds DMA-friendly block for the mailbox */ > void *mbox;