From patchwork Fri Sep 24 10:29:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 12514983 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1C754C433F5 for ; Fri, 24 Sep 2021 10:30:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 030DB61164 for ; Fri, 24 Sep 2021 10:30:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240270AbhIXKbm (ORCPT ); Fri, 24 Sep 2021 06:31:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:36708 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231140AbhIXKbl (ORCPT ); Fri, 24 Sep 2021 06:31:41 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 02A0061164; Fri, 24 Sep 2021 10:30:09 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94.2) (envelope-from ) id 1mTiT1-003KSl-RS; Fri, 24 Sep 2021 06:30:07 -0400 Message-ID: <20210924102917.106053441@goodmis.org> User-Agent: quilt/0.66 Date: Fri, 24 Sep 2021 06:29:17 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Masami Hiramatsu , Mathieu Desnoyers , linux-trace-devel@vger.kernel.org Subject: [PATCH 0/2 v2] tracing: Have trace_pid_list be a sparse array Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org When the trace_pid_list was created, the default pid max was 32768. Creating a bitmask that can hold one bit for all 32768 took up 4096 (one page). Having a one page bitmask was not much of a problem, and that was used for mapping pids. But today, systems are bigger and can run more tasks, and now the default pid_max is usually set to 4194304. Which means to handle that many pids requires 524288 bytes. Worse yet, the pid_max can be set to 2^30 (1073741824 or 1G) which would take 134217728 (128M) of memory to store this array. Since the pid_list array is very sparsely populated, it is a huge waste of memory to store all possible bits for each pid when most will not be set. Instead, use a page table scheme to store the array, and allow this to handle up to 30 bit pids. The pid_mask will start out with 256 entries for the first 8 MSB bits. This will cost 1K for 32 bit architectures and 2K for 64 bit. Each of these will have a 256 array to store the next 8 bits of the pid (another 1 or 2K). These will hold an 2K byte bitmask (which will cover the LSB 14 bits or 16384 pids). When the trace_pid_list is allocated, it will have the 1/2K upper bits allocated, and then it will allocate a cache for the next upper chunks and the lower chunks (default 6 of each). Then when a bit is "set", these chunks will be pulled from the free list and added to the array. If the free list gets down to a lever (default 2), it will trigger an irqwork that will refill the cache back up. On clearing a bit, if the clear causes the bitmask to be zero, that chunk will then be placed back into the free cache for later use, keeping the need to allocate more down to a minimum. Changes since v1: https://lore.kernel.org/all/20210924033547.939554938@goodmis.org/ - Changed the bit split from 10,10,12 to 8,8,14 and only check the 30 bits of the pid, as according to linux/thread.h a pid may only be at most 30 bits. - Added a WARN_ON_ONCE(pid_max > (1 << 30)) to be sure. Steven Rostedt (VMware) (2): tracing: Place trace_pid_list logic into abstract functions tracing: Create a sparse bitmask for pid filtering ---- kernel/trace/Makefile | 1 + kernel/trace/ftrace.c | 6 +- kernel/trace/pid_list.c | 557 ++++++++++++++++++++++++++++++++++++++++++++ kernel/trace/trace.c | 78 +++---- kernel/trace/trace.h | 14 +- kernel/trace/trace_events.c | 6 +- 6 files changed, 601 insertions(+), 61 deletions(-) create mode 100644 kernel/trace/pid_list.c