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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8DD0DC43219 for ; Thu, 13 Oct 2022 18:02:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230354AbiJMSCM (ORCPT ); Thu, 13 Oct 2022 14:02:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230384AbiJMSBs (ORCPT ); Thu, 13 Oct 2022 14:01:48 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62595160EDF; Thu, 13 Oct 2022 11:01:25 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 281516192D; Thu, 13 Oct 2022 17:57:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30B6EC433C1; Thu, 13 Oct 2022 17:57:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1665683855; bh=uIlkY5Zeiam6CYpFKVqUgIhLspxK9NxVICIPnnLsybs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=X8kWtT6WKEzCMZbkPgJ82m8le34k7usL7pfm8iF1FVl1LOY5Hq2Yuf4yzZXGtCHy7 /rlH+71TLCAzLctgaME4w7oP06OyBAto8i5jKeB+xLF7nzYZw78KdupufLHPGMfqRj mbSjeSJOhOx8vb4PovHiw8TI5mMHGhDtX85hzVYs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sebastian Andrzej Siewior , "Jason A. Donenfeld" Subject: [PATCH 5.15 14/27] random: avoid reading two cache lines on irq randomness Date: Thu, 13 Oct 2022 19:52:43 +0200 Message-Id: <20221013175144.060241859@linuxfoundation.org> X-Mailer: git-send-email 2.38.0 In-Reply-To: <20221013175143.518476113@linuxfoundation.org> References: <20221013175143.518476113@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jason A. Donenfeld commit 9ee0507e896b45af6d65408c77815800bce30008 upstream. In order to avoid reading and dirtying two cache lines on every IRQ, move the work_struct to the bottom of the fast_pool struct. add_ interrupt_randomness() always touches .pool and .count, which are currently split, because .mix pushes everything down. Instead, move .mix to the bottom, so that .pool and .count are always in the first cache line, since .mix is only accessed when the pool is full. Fixes: 58340f8e952b ("random: defer fast pool mixing to worker") Reviewed-by: Sebastian Andrzej Siewior Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -894,10 +894,10 @@ void __init add_bootloader_randomness(co } struct fast_pool { - struct work_struct mix; unsigned long pool[4]; unsigned long last; unsigned int count; + struct work_struct mix; }; static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {