Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751764AbaDYVXI (ORCPT ); Fri, 25 Apr 2014 17:23:08 -0400 Received: from mail-pb0-f50.google.com ([209.85.160.50]:64745 "EHLO mail-pb0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750993AbaDYVXG (ORCPT ); Fri, 25 Apr 2014 17:23:06 -0400 Message-ID: <535AD235.90604@kernel.dk> Date: Fri, 25 Apr 2014 15:23:01 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Ming Lei CC: Alexander Gordeev , Linux Kernel Mailing List , Kent Overstreet , Shaohua Li , Nicholas Bellinger , Ingo Molnar , Peter Zijlstra Subject: Re: [PATCH RFC 0/2] percpu_ida: Take into account CPU topology when stealing tags References: <20140422071057.GA13195@dhcp-26-169.brq.redhat.com> <535676A1.3070706@kernel.dk> <5356916F.4000205@kernel.dk> <535716A5.6050108@kernel.dk> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/25/2014 03:10 AM, Ming Lei wrote: > Hi Jens, > > On Wed, Apr 23, 2014 at 9:25 AM, Jens Axboe wrote: >> On 2014-04-22 18:53, Ming Lei wrote: >> >> >>> In my null_blk test on a quad core SMP VM: >>> >>> - 4 hw queue >>> - timer mode >>> >>> With the above approach, tag allocation from local CPU can be >>> improved from: >>> >>> 5% -> 50% for boot CPU >>> 30% -> 90% for non-boot CPU. >>> >>> If no one objects the idea, I'd like to post a patch for review. >> >> >> Sent it out, that can't hurt. I'll take a look at it, and give it a test >> spin as well. > > I have sent out the patch in below link, and appreciate much > you will take a look at it. > > marc.info/?l=linux-kernel&m=139826944613225&w=2 Sorry, I did run it the other day. It has little to no effect here, but that's mostly because there's so much other crap going on in there. The most effective way to currently make it work better, is just to ensure the caching pool is of a sane size. I've got an alternative tagging scheme that I think would be useful for the cases where the tag space to cpu ratio isn't big enough. So I think we'll retain percpu_ida for the cases where it can cache enough, and punt to an alternative scheme when not. That doesn't mean we should not improve percpu_ida. There's quite a bit of low hanging fruit in there. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/