From mboxrd@z Thu Jan 1 00:00:00 1970 From: hch@infradead.org (Christoph Hellwig) Date: Tue, 23 May 2017 00:17:05 -0700 Subject: NVMe APST high latency power states being skipped In-Reply-To: References: Message-ID: <20170523071705.GD16776@infradead.org> On Mon, May 22, 2017@05:04:15PM +0800, Kai-Heng Feng wrote: > Hi Andy, > > Currently, if a power state tradition requires high latency, it may be > skipped [1] based on the value of ps_max_latency_us in > nvme_configure_apst(): > > if (total_latency_us > ctrl->ps_max_latency_us) > continue; > > Right now ps_max_latency_us defaults to 25000, but some consumer level > NVMe have much higher latency. > I understand this value is configurable, but I am wondering if it's > possible to ignore the latency on consumer devices, probably based on > chassis type, so consumer devices can get most NVMe power saving out > of the box? What is your proposed change? Do you have any numbers on how this improves power consumption for given workloads and what the performance impact is on common benchmarks?