From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-trace-users-owner@vger.kernel.org Received: from smtprelay0179.hostedemail.com ([216.40.44.179]:47838 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933182AbcDSTlR (ORCPT ); Tue, 19 Apr 2016 15:41:17 -0400 Date: Tue, 19 Apr 2016 15:41:13 -0400 From: Steven Rostedt To: "H. Peter Anvin" Cc: Mathieu Desnoyers , linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Thomas Gleixner , Jiri Olsa , Masami Hiramatsu , Namhyung Kim , linux-trace-users@vger.kernel.org Subject: Re: [RFC][PATCH 2/4] tracing: Use pid bitmap instead of a pid array for set_event_pid Message-ID: <20160419154113.64f146dc@grimm.local.home> In-Reply-To: <4ACF15B6-D344-4647-9CF8-CEDE5BF5EF70@zytor.com> References: <20160419143421.829909157@goodmis.org> <20160419143725.295928551@goodmis.org> <1694657549.62933.1461084928341.JavaMail.zimbra@efficios.com> <20160419131947.3c5208b4@gandalf.local.home> <4ACF15B6-D344-4647-9CF8-CEDE5BF5EF70@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-trace-users-owner@vger.kernel.org List-ID: On Tue, 19 Apr 2016 11:57:32 -0700 "H. Peter Anvin" wrote: > Also, I understand there is one of these bitmaps per ring buffer, and > the ring buffer is in the tens of megabytes. Right, there's only one bitmap per tracing instance, which in most cases is just one (I know of people who make more). And by default, the tracing buffer is 1.4 megs per CPU. If you have a pid_max of the max size, I highly doubt you will be doing that on a single CPU machine. If you have 48 CPUs, the ring buffer will be 1.4 * 48 megs, making the 1/2 meg bitmap a nit. I will say, there may be two bitmaps soon, because I plan on adding this same code to the function tracer logic. -- Steve