Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <f3c045a6-2ed9-c948-04c9-325649b1dfe0@bytedance.com>
Date:   Wed, 6 Jul 2022 17:51:03 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0)
 Gecko/20100101 Thunderbird/91.11.0
Subject: Re: [PATCH v4 0/7] sched/fair: improve scan efficiency of SIS
Content-Language: en-US
To:     Peter Zijlstra <peterz@infradead.org>,
        Mel Gorman <mgorman@suse.de>,
        Vincent Guittot <vincent.guittot@linaro.org>
Cc:     Josh Don <joshdon@google.com>, Chen Yu <yu.c.chen@intel.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        "Gautham R . Shenoy" <gautham.shenoy@amd.com>,
        linux-kernel@vger.kernel.org
References: <20220619120451.95251-1-wuyun.abel@bytedance.com>
From:   Abel Wu <wuyun.abel@bytedance.com>
In-Reply-To: <20220619120451.95251-1-wuyun.abel@bytedance.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

Gentle ping

On 6/19/22 8:04 PM, Abel Wu Wrote:
> The wakeup fastpath (select_idle_sibling or SIS) plays an important role
> in maximizing the usage of cpu resources and can greatly affect overall
> performance of the system.
> 
> The SIS tries to find an idle cpu inside that LLC to place the woken-up
> task. The cache hot cpus will be checked first, then other cpus of that
> LLC (domain scan) if the hot ones are not idle.
> 
> The domain scan works well under light workload by simply traversing
> the cpus of the LLC due to lots of idle cpus can be available. But this
> doesn’t scale well once the LLC gets bigger and the load increases, so
> SIS_PROP was born to limit the scan cost. For now SIS_PROP just limits
> the number of cpus to be scanned, but the way of how it scans is not
> changed.
> 
> This patchset introduces the SIS filter to help improving scan efficiency
> when scan depth is limited. The filter only contains the unoccupied cpus,
> and is updated during SMT level load balancing. It is expected that the
> more overloaded the system is, the less cpus will be scanned.
> 
> ...
>