From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759984Ab3GSI2z (ORCPT ); Fri, 19 Jul 2013 04:28:55 -0400 Received: from mail-ea0-f182.google.com ([209.85.215.182]:33231 "EHLO mail-ea0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755211Ab3GSI2w (ORCPT ); Fri, 19 Jul 2013 04:28:52 -0400 Date: Fri, 19 Jul 2013 10:28:48 +0200 From: Ingo Molnar To: Andrew Morton Cc: Dave Hansen , linux-kernel@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org, Peter Zijlstra Subject: Re: [RESEND][PATCH] mm: vmstats: tlb flush counters Message-ID: <20130719082848.GA25784@gmail.com> References: <20130716234438.C792C316@viggo.jf.intel.com> <20130717072100.GA14359@gmail.com> <20130718135157.2262e28b2c6e0f43a4d0fe7a@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130718135157.2262e28b2c6e0f43a4d0fe7a@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Morton wrote: > On Wed, 17 Jul 2013 09:21:00 +0200 Ingo Molnar wrote: > > > > > * Dave Hansen wrote: > > > > > I was investigating some TLB flush scaling issues and realized > > > that we do not have any good methods for figuring out how many > > > TLB flushes we are doing. > > > > > > It would be nice to be able to do these in generic code, but the > > > arch-independent calls don't explicitly specify whether we > > > actually need to do remote flushes or not. In the end, we really > > > need to know if we actually _did_ global vs. local invalidations, > > > so that leaves us with few options other than to muck with the > > > counters from arch-specific code. > > Spose so, if you really think it's worth it. It's all downside for > uniprocessor machines. [...] UP is slowly going extinct, but in any case these counters ought to inform us about TLB flushes even on UP systems: > > > + NR_TLB_LOCAL_FLUSH_ALL, > > > + NR_TLB_LOCAL_FLUSH_ONE, > > > + NR_TLB_LOCAL_FLUSH_ONE_KERNEL, While these ought to be compiled out on UP kernels: > > > + NR_TLB_REMOTE_FLUSH, /* cpu tried to flush others' tlbs */ > > > + NR_TLB_REMOTE_FLUSH_RECEIVED,/* cpu received ipi for flush */ Right? > > Please fix the vertical alignment of comments. > > I looked - this isn't practical. > > It would be nice to actually document these things though. We don't > *have* to squeeze the comment into the RHS. Agreed. Thanks, Ingo