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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2E41C433F5 for ; Thu, 14 Oct 2021 08:41:59 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0391360F9E for ; Thu, 14 Oct 2021 08:41:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0391360F9E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4HVNDj56kPz3bXc for ; Thu, 14 Oct 2021 19:41:57 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=TsvQCRJ7; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linuxfoundation.org (client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=gregkh@linuxfoundation.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=TsvQCRJ7; dkim-atps=neutral Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4HVNCz4Zs0z2yPS for ; Thu, 14 Oct 2021 19:41:18 +1100 (AEDT) Received: by mail.kernel.org (Postfix) with ESMTPSA id 1338D60F9E; Thu, 14 Oct 2021 08:41:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1634200875; bh=rY9vGtlLDIvkDgY0wX20Oxpih5WsKZMgiPYMwz/VsXE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TsvQCRJ72G2+iekhh/WK3vT5lHlv7ZD6YNQNgAj3L2thXFnBxsGvyUNRW7BamuMqV 1IPExSgJeQI9q0Wym4ATW8HhvO4Aw4CJX4+DsF+KHwMiO6IDjMMu0SjL/bAsfi1hLh r4jkVd+UWyWv+rIV5buFUYY+dM3WYR0t5NCyZNCs= Date: Thu, 14 Oct 2021 10:41:13 +0200 From: Greg KH To: Xianting Tian Subject: Re: [PATCH v10 2/3] tty: hvc: pass DMA capable memory to put_chars() Message-ID: References: <20211009114829.1071021-1-xianting.tian@linux.alibaba.com> <20211009114829.1071021-3-xianting.tian@linux.alibaba.com> <3516c58c-e8e6-2e5a-2bc8-ad80e2124d37@linux.alibaba.com> <4dbeddb9-1068-d282-2758-55d0f788ea61@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4dbeddb9-1068-d282-2758-55d0f788ea61@linux.alibaba.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: arnd@arndb.de, amit@kernel.org, jirislaby@kernel.org, shile.zhang@linux.alibaba.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, osandov@fb.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Oct 14, 2021 at 04:34:59PM +0800, Xianting Tian wrote: > > 在 2021/10/10 下午1:33, Greg KH 写道: > > On Sat, Oct 09, 2021 at 11:45:23PM +0800, Xianting Tian wrote: > > > 在 2021/10/9 下午7:58, Greg KH 写道: > > > > Did you look at the placement using pahole as to how this structure now > > > > looks? > > > thanks for all your commnts. for this one, do you mean I need to remove the > > > blank line? thanks > > > > > No, I mean to use the tool 'pahole' to see the structure layout that you > > just created and determine if it really is the best way to add these new > > fields, especially as you are adding huge buffers with odd alignment. > > thanks, > > Based on your comments, I removed 'char outchar', remian the position of > 'int outbuf_size' unchanged to keep outbuf_size and lock in the same cache > line. Now hvc_struct change as below, > > struct hvc_struct { > struct tty_port port; > spinlock_t lock; > int index; > int do_wakeup; > - char *outbuf; > int outbuf_size; > int n_outbuf; > uint32_t vtermno; > @@ -48,6 +57,16 @@ struct hvc_struct { > struct work_struct tty_resize; > struct list_head next; > unsigned long flags; > + > + /* > + * the buf is used in hvc console api for putting chars, > + * and also used in hvc_poll_put_char() for putting single char. > + */ > + char cons_outbuf[N_OUTBUF] __ALIGNED__; > + spinlock_t cons_outbuf_lock; > + > + /* the buf is used for putting chars to tty */ > + char outbuf[] __ALIGNED__; > }; > > pahole for above hvc_struct as below, is it ok for you? do we need to pack > the hole? thanks > > struct hvc_struct { > struct tty_port port; /* 0 352 */ > /* --- cacheline 5 boundary (320 bytes) was 32 bytes ago --- */ > spinlock_t lock; /* 352 4 */ > int index; /* 356 4 */ > int do_wakeup; /* 360 4 */ > int outbuf_size; /* 364 4 */ > int n_outbuf; /* 368 4 */ > uint32_t vtermno; /* 372 4 */ > const struct hv_ops * ops; /* 376 8 */ > /* --- cacheline 6 boundary (384 bytes) --- */ > int irq_requested; /* 384 4 */ > int data; /* 388 4 */ > struct winsize ws; /* 392 8 */ > struct work_struct tty_resize; /* 400 32 */ > struct list_head next; /* 432 16 */ > /* --- cacheline 7 boundary (448 bytes) --- */ > long unsigned int flags; /* 448 8 */ > > /* XXX 56 bytes hole, try to pack */ > > /* --- cacheline 8 boundary (512 bytes) --- */ > char cons_outbuf[16]; /* 512 16 */ > spinlock_t cons_outbuf_lock; /* 528 4 */ > > /* XXX 44 bytes hole, try to pack */ Why not move the spinlock up above the cons_outbuf? Will that not be a bit better? Anyway, this is all fine, and much better than before, thanks. greg k-h