Received-SPF: pass (google.com: domain of linux-kernel+bounces-93702-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Message-ID: <0914758f-f492-8cb5-2bd2-c13473c32e48@amd.com>
Date: Wed, 6 Mar 2024 15:34:47 +0530
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.13.1
Subject: Re: [RFC PATCH 00/14] Introducing TIF_NOTIFY_IPI flag
Content-Language: en-US
To: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-kernel@vger.kernel.org, "Gautham R. Shenoy"
 <gautham.shenoy@amd.com>, Richard Henderson <richard.henderson@linaro.org>,
 Russell King <linux@armlinux.org.uk>, Ingo Molnar <mingo@redhat.com>,
 Peter Zijlstra <peterz@infradead.org>, Juri Lelli <juri.lelli@redhat.com>,
 Vincent Guittot <vincent.guittot@linaro.org>,
 Dietmar Eggemann <dietmar.eggemann@arm.com>, Ard Biesheuvel
 <ardb@kernel.org>, Arnd Bergmann <arnd@arndb.de>, x86@kernel.org,
 linux-arm-kernel@lists.infradead.org
References: <20240220171457.703-1-kprateek.nayak@amd.com>
 <CACRpkdbxjU0r+PDTxJwrgzuJgaKnOCHtkaZtm4jO6bmFQ0SPiQ@mail.gmail.com>
From: K Prateek Nayak <kprateek.nayak@amd.com>
In-Reply-To: <CACRpkdbxjU0r+PDTxJwrgzuJgaKnOCHtkaZtm4jO6bmFQ0SPiQ@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0:
	=?utf-8?B?bHhDeHZWV2pyYy85bEFMc0hIZXJJQlRvNmw0cVQxb3N5NHhwV21jaFZWbE13?=
 =?utf-8?B?T0MrbTIvQ1A3SmJSR0NjenJ0MGd3TndlQys5N2dTNlhZUVlBcmFDMXdiL1pv?=
 =?utf-8?B?L2paMFJOODFxRkxnU2ljRkp3cHpWT1ZiVzV5aXlrc3RsZ2xmNmtsRExHMHR1?=
 =?utf-8?B?cUpWOFlycHl2MWcvRHFpMTdQUzUrdFo5V1NmOG5lMkFNenlQaFVkcEhDQjY1?=
 =?utf-8?B?TlVqTGN3QnJ4UnVOL0J3Vmo4N0Jzak1UbUVRaEl0UVN0VFIxM00xdW1aT21D?=
 =?utf-8?B?cjUva28wbTRpczI1ZUt3NzBDZis1dFFUMmJMaGwxRDk3SWF4ZlNDaW0rMkc2?=
 =?utf-8?B?SWJjSVdMakdFd0hwWGtIUGZsVXFOdkhrTTc2WG9qa05pREVkK3pRend6VFBw?=
 =?utf-8?B?THdadkVLM3lTcExhZW1ERE1XYjFEbE4vTDc0eDZCOVppS0NFYWJBcUtsVjVJ?=
 =?utf-8?B?OEFEc29TdE1zYlNJNiszcGR2ZWxSdHNyN3BjdmNOekZRblBYR3h1eExYaW9j?=
 =?utf-8?B?L1pKU1loQUFTZVlJeEFmMDlYU1UzelhPRmpaUHY0UTNhU2FMbjRObWlaN0Fj?=
 =?utf-8?B?UW15by9Wd3FFM0hING5mZWtucWlETitEUVJ6L0dHN3hlNVl1ZFh3aDRISlpX?=
 =?utf-8?B?VXFreUEyK2xlZjFpNTJlK1d3cUhhVTFCcUYwUFlZcDhTMllEamFqL3JMS2dY?=
 =?utf-8?B?QzZCYkNwOFBvbUp1eVRkUzNQOGhrVnFPbkg1MFRxdGxjNkFIa0djTndLN1lB?=
 =?utf-8?B?KzhYNkhRYlpiK2FoUFc1bmxYWlhNNW9PT3doYWlSOEFiWVFhbUtVWTFkSGF1?=
 =?utf-8?B?YTJaOFhNa2xoU29WalhxYXZ4cGNIVGoyZUhYbEd1NHpVblRwNDdTdllsR0FS?=
 =?utf-8?B?dlNhZ3VnQmZKVWxyckpSc2JXaGMvQklXRE52NWVHd0EyNlpkSjlTOG5oS0t0?=
 =?utf-8?B?Q2FBb2daM01nWG5LOHZjY2xiU01SaFZBTmF6aGZ6eVZvdHhFMTRXYXkraGM5?=
 =?utf-8?B?RlJFNEpJay9FbDhzM3JmdXJnZmNaSWZpcy9oanJ3djFGY2tHd1BPOXNUNWtq?=
 =?utf-8?B?YjJLemhhbFpuemFtbzVxN3ZIYUNsTzJ6Z3IrVktyNEFjck5ZWG9lRkFkRjBO?=
 =?utf-8?B?MFV5SVR4a25KZDk4WWtrc3VWR25MeDJXOHlZcUFpQmp4UlFGZ1BqUVVXaWdr?=
 =?utf-8?B?NmVXV0FzMy9yM3FESGh3U0RZS0hxYlJqc3NEVk5ySzNvVGdKRGtqN203VW5q?=
 =?utf-8?B?MnVsZDI1UEZHeWxaMkUvWGZYV1FrcUlNeitPa0xjb3JzZWE5N3FIUFFsSXpn?=
 =?utf-8?B?OEZGc0xveEE0bklMWXg0aDRkUTI4TnpPUjlYaE9RL1ZnNzFYR1ovK1AwTjZi?=
 =?utf-8?B?WjZyd0dGUVNCbHMyZUpaNDIxcUptQk1OcXpiMXRCdGRuK1JKMnJ4U1RKRHpu?=
 =?utf-8?B?SmluU1ExVTNJbGlTK1V6eHd2SGtPM2o5eHBydzFUMnU5WUl1eFNpS2w3a0sy?=
 =?utf-8?B?a1A0NlhyZjlMaVF6WVRUQS9FRmlRV0xUZzRCZm9tWjA0RUsrTG9UekVEa2Z0?=
 =?utf-8?B?Zlc3bTlOaktQZVRYZmpJSnFqbVUvZUtncmszQjY0YXgvcHVIQ3U0ZkFqSlhn?=
 =?utf-8?B?ZjRnOEZFQmxQSEZUNTVZS1NMc0pyd1FUTm4wdHYzTUFYSEpuWVZLUnpQSzky?=
 =?utf-8?B?NC9zMk5peEtlZnRLVkp1cy9iMnV1UUFxZVpmSEVna05lNTBFdTZjeHoxbHUx?=
 =?utf-8?B?ek0vMzUrQkJhM2hSRVlHVURqUXhrT2RVVEo5U1BXdFZyTUgzWHNwUzN0VkFp?=
 =?utf-8?B?Lzl3U2xpYnYrNzJ5ak43V1RGRGRuUmFqSWdtMCs4d1ZLTXkyRHVJZTZxcGJK?=
 =?utf-8?B?Z2dXTFpCRE8ya1FxTmhrNUtBWTN6SmFoZVgxVzFJM3hkYThIOHlFcnZtNzMx?=
 =?utf-8?B?djlpbUlEaTJ6WFJ4M244Q0pwdFhORlc4RXB6R1ExZG9uK3pOMU5sclRla2pu?=
 =?utf-8?B?ejVYUno3dlR4YitEbThzSmZLWGZ0UHFaYnE3SFlYWDQydXo4Vmd6VlVuYnFR?=
 =?utf-8?B?NTFRODZZTG5pd1ZyWkdmNjlpTlc3cDdtVi9SYStlNHVONXhpNjJ4ajczTEI3?=
 =?utf-8?Q?i1tiZPlZZV8vPpNvL6bCgHVEN?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: a13ce31f-4652-415f-4601-08dc3dc4e0e5
X-MS-Exchange-CrossTenant-AuthSource: MW2PR12MB2379.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Mar 2024 10:04:57.9034
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: GoaenpiviY9ISs5kmpAp9bmInGm08rkjZLa7jGvu6u4uMeMZ0U3J63t7NGSHJDkxZeSa8i09XahFZxJvwxVOaA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB7672

Hello Linus,

Thank you for taking a look at the patch.

On 3/6/2024 3:14 PM, Linus Walleij wrote:
> Hi K Prateek,
> 
> I trimmed down the recipient list so we don't bounce.
> 
> On Tue, Feb 20, 2024 at 6:15 PM K Prateek Nayak <kprateek.nayak@amd.com> wrote:
> 
>> Same experiment was repeated on an dual socket ARM server (2 x 64C)
>> which too saw a significant improvement in the ipistorm performance:
>>
>>   ==================================================================
>>   Test          : ipistorm (modified)
>>   Units         : Normalized runtime
>>   Interpretation: Lower is better
>>   Statistic     : AMean
>>   ==================================================================
>>   kernel:                               time [pct imp]
>>   tip:sched/core                        1.00 [0.00]
>>   tip:sched/core + TIF_NOTIFY_IPI       0.41 [59.29]
> 
> Is that a 64bit ARM64 system or really an ARM 32-bit 64-core system?
> 
> I'm confused because:
> 
>> K Prateek Nayak (10):
>>   arm/thread_info: Introduce TIF_NOTIFY_IPI flag
> 
> There is no arm64 patch in the patch series.

When I started out, assumed both arm32 and arm64 shared the same
thread_info file. I basically ran:

	$ grep -r "TIF_POLLING_NRFLAG" arch/arm*
	arch/arm/include/asm/thread_info.h: *  TIF_POLLING_NRFLAG       - true if poll_idle() is polling TIF_NEED_RESCHED

and reached here but now I see "arch/arm64/include/asm/thread_info.h".
The machine I tested on was "aarch64" and was listed "Neoverse-N1" as
the "Model name" when running lscpu. This series changes some behavior
around IPI delivery to an idle thread but without "TIF_POLLING_NRFLAG"
defined, the behavior should remain same. I have limited access to the
server I tested on. Let me see if I can get some cycles to test this
once again.

> 
> I can perhaps test the patches on an ARM32 system but all I have is dualcore
> I think.
> 
> Yours,
> Linus Walleij

--
Thanks and Regards,
Prateek