From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751320AbeDGHy4 (ORCPT ); Sat, 7 Apr 2018 03:54:56 -0400 Received: from mga12.intel.com ([192.55.52.136]:6311 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751031AbeDGHyz (ORCPT ); Sat, 7 Apr 2018 03:54:55 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.48,418,1517904000"; d="scan'208";a="31746042" Subject: Re: [PATCH ipmi/kcs_bmc v1] ipmi: kcs_bmc: optimize the data buffers allocation From: "Wang, Haiyue" To: minyard@acm.org, openipmi-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <1521116452-4993-1-git-send-email-haiyue.wang@linux.intel.com> Message-ID: <1710edd4-277b-1d2e-5885-a070751ddd2a@linux.intel.com> Date: Sat, 7 Apr 2018 15:54:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Corey, Since IPMI 2.0 just defined minimum, no maximum: ---- KCS/SMIC Input : Required: 40 bytes IPMI Message, minimum KCS/SMIC Output : Required: 38 bytes IPMI Message, minimum ---- We can enlarge the block size for avoiding waste, and make our driver support most worst message size case. And I think this patch make checking simple (from 3 to 1), and the code clean, this is the biggest reason I want to change. The TLB is just memory management study from book, no data to support access improvement. :) BR, Haiyue On 2018-04-07 10:37, Wang, Haiyue wrote: > > > On 2018-04-07 05:47, Corey Minyard wrote: >> On 03/15/2018 07:20 AM, Haiyue Wang wrote: >>> Allocate a continuous memory block for the three KCS data buffers with >>> related index assignment. >> >> I'm finally getting to this. >> >> Is there a reason you want to do this?  In general, it's better to >> not try to >> outsmart your base system.  Depending on the memory allocator, in this >> case, you might actually use more memory.  You probably won't use any >> less. >> > I got this idea from another code review, but that patch allocates 30 > more > the same size memory block, reducing the devm_kmalloc call will be > better. > For KCS only have 3, may be the key point is memory waste. > >> In the original case, you allocate three 1000 byte buffers, resulting >> in 3 >> 1024 byte slab allocated. >> >> In the changed case, you will allocate a 3000 byte buffer, resulting in >> a single 4096 byte slab allocation, wasting 1024 more bytes of memory. >> > As the kcs has memory copy between in/out/kbuffer, put them in the same > page will be better ? Such as the same TLB ? (Well, I just got this > from book, > no real experience of memory accessing performance. And also, I was told > that using space to save the time. :-)). > > Just my stupid thinking. I'm OK to drop this patch if it doesn't help > with > performance, or something else. > > BR. > Haiyue > >> -corey >> >>> Signed-off-by: Haiyue Wang >>> --- >>>   drivers/char/ipmi/kcs_bmc.c | 10 ++++++---- >>>   1 file changed, 6 insertions(+), 4 deletions(-) >>> >>> diff --git a/drivers/char/ipmi/kcs_bmc.c b/drivers/char/ipmi/kcs_bmc.c >>> index fbfc05e..dc19c0d 100644 >>> --- a/drivers/char/ipmi/kcs_bmc.c >>> +++ b/drivers/char/ipmi/kcs_bmc.c >>> @@ -435,6 +435,7 @@ static const struct file_operations kcs_bmc_fops >>> = { >>>   struct kcs_bmc *kcs_bmc_alloc(struct device *dev, int sizeof_priv, >>> u32 channel) >>>   { >>>       struct kcs_bmc *kcs_bmc; >>> +    void *buf; >>>         kcs_bmc = devm_kzalloc(dev, sizeof(*kcs_bmc) + sizeof_priv, >>> GFP_KERNEL); >>>       if (!kcs_bmc) >>> @@ -448,11 +449,12 @@ struct kcs_bmc *kcs_bmc_alloc(struct device >>> *dev, int sizeof_priv, u32 channel) >>>       mutex_init(&kcs_bmc->mutex); >>>       init_waitqueue_head(&kcs_bmc->queue); >>>   -    kcs_bmc->data_in = devm_kmalloc(dev, KCS_MSG_BUFSIZ, >>> GFP_KERNEL); >>> -    kcs_bmc->data_out = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL); >>> -    kcs_bmc->kbuffer = devm_kmalloc(dev, KCS_MSG_BUFSIZ, GFP_KERNEL); >>> -    if (!kcs_bmc->data_in || !kcs_bmc->data_out || !kcs_bmc->kbuffer) >>> +    buf = devm_kmalloc_array(dev, 3, KCS_MSG_BUFSIZ, GFP_KERNEL); >>> +    if (!buf) >>>           return NULL; >>> +    kcs_bmc->data_in  = buf; >>> +    kcs_bmc->data_out = buf + KCS_MSG_BUFSIZ; >>> +    kcs_bmc->kbuffer  = buf + KCS_MSG_BUFSIZ * 2; >>>         kcs_bmc->miscdev.minor = MISC_DYNAMIC_MINOR; >>>       kcs_bmc->miscdev.name = dev_name(dev); >> >> >