From mboxrd@z Thu Jan 1 00:00:00 1970 From: "majun (Euler7)" Subject: Re: [RFC PATCH 0/3] Add a new flag for ITS device to control indirect route Date: Mon, 5 Dec 2016 11:11:28 +0800 Message-ID: <5844DAE0.9050101@huawei.com> References: <1480578360-9268-1-git-send-email-majun258@huawei.com> <3ce161a7-ee63-a018-4a75-9e7520143d97@arm.com> <58413F0E.3030604@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Return-path: Received: from szxga02-in.huawei.com ([119.145.14.65]:24564 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751120AbcLEDLz (ORCPT ); Sun, 4 Dec 2016 22:11:55 -0500 In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Marc Zyngier , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, robert.moore@intel.com, lenb@kernel.org, lv.zheng@intel.com, rafael.j.wysocki@intel.com, devel@acpica.org, mark.rutland@arm.com, robh+dt@kernel.org, jason@lakedaemon.net Cc: majun258@huawei.com, dingtianhong@huawei.com, guohanjun@huawei.com Hi Marc: 在 2016/12/2 17:35, Marc Zyngier 写道: > On 02/12/16 09:29, majun (Euler7) wrote: >> >> >> 在 2016/12/1 17:07, Marc Zyngier 写道: >>> On 01/12/16 07:45, Majun wrote: >>>> From: MaJun >>>> >>>> For current ITS driver, two level table (indirect route) is enabled when the memory used >>>> for LPI route table over the limit(64KB * 2) size. But this function impact the >>>> performance of LPI interrupt actually because need more time to look up the table. >>> >>> Are you implying that your ITS doesn't have a cache to lookup the most >>> active devices, hence performing a full lookup on each interrupt? >> >> Our ITS chip has the cache with depth 64. But this seems not enough for some >> scenario,espeically on virtulization platform. > > Then I don't see how switching to to flat tables is going to improve > things. Can you share actual performance numbers? > Sorry, I run this code on EMU and have no actual performance numbers now. Suppose there are 66 devices in system. As far as our chip concerned, there are always 2 devices can't benefit from cache fully when they report the interrupt. If i'm wrong, please correct me. Thanks Majun >>> Anyway, doing this as a DT quirk doesn't feel right. Please use the ITS >>> quirk infrastructure. >> >> If there is no other better solutions, I will do this. > > Thanks, > > M. >