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 5CF6DC433F5 for ; Thu, 14 Oct 2021 08:56:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3E405610EA for ; Thu, 14 Oct 2021 08:56:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230007AbhJNI6P (ORCPT ); Thu, 14 Oct 2021 04:58:15 -0400 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:50888 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229912AbhJNI6N (ORCPT ); Thu, 14 Oct 2021 04:58:13 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=xianting.tian@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0Urmp48k_1634201765; Received: from B-LB6YLVDL-0141.local(mailfrom:xianting.tian@linux.alibaba.com fp:SMTPD_---0Urmp48k_1634201765) by smtp.aliyun-inc.com(127.0.0.1); Thu, 14 Oct 2021 16:56:06 +0800 Subject: Re: [PATCH v10 2/3] tty: hvc: pass DMA capable memory to put_chars() To: Greg KH Cc: jirislaby@kernel.org, amit@kernel.org, arnd@arndb.de, osandov@fb.com, shile.zhang@linux.alibaba.com, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org 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> From: Xianting Tian Message-ID: <8225536f-8ecb-0678-f630-265652793a42@linux.alibaba.com> Date: Thu, 14 Oct 2021 16:56:05 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/10/14 下午4:41, Greg KH 写道: > 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? thanks, I will move it avove cons_outbuf, and send v11 patches soon. > > Anyway, this is all fine, and much better than before, thanks. > > greg k-h