From mboxrd@z Thu Jan 1 00:00:00 1970 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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED 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 BEBB4C48BD1 for ; Wed, 9 Jun 2021 22:05:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A0F57613F2 for ; Wed, 9 Jun 2021 22:05:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230313AbhFIWHg (ORCPT ); Wed, 9 Jun 2021 18:07:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:51928 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229788AbhFIWHe (ORCPT ); Wed, 9 Jun 2021 18:07:34 -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 28AC3613DF; Wed, 9 Jun 2021 22:05:39 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94.2) (envelope-from ) id 1lr6KQ-002aTR-2x; Wed, 09 Jun 2021 18:05:38 -0400 Message-ID: <20210609220537.927890401@goodmis.org> User-Agent: quilt/0.66 Date: Wed, 09 Jun 2021 18:04:58 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Linus Torvalds , Ingo Molnar , Andrew Morton Subject: [PATCH 1/2] tracing: Simplify the max length test when using the filtering temp buffer References: <20210609220457.220164154@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (VMware)" When filtering trace events, a temp buffer is used because the extra copy from the temp buffer into the ring buffer is still faster than the direct write into the ring buffer followed by a discard if the filter does not match. But the data that can be stored in the temp buffer is a PAGE_SIZE minus the ring buffer event header. The calculation of that header size is complex, but using the helper macro "struct_size()" can simplify it. Link: https://lore.kernel.org/stable/CAHk-=whKbJkuVmzb0hD3N6q7veprUrSpiBHRxVY=AffWZPtxmg@mail.gmail.com/ Suggested-by: Linus Torvalds Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index f6c4d9cf0377..7f198d8959f2 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2737,8 +2737,10 @@ trace_event_buffer_lock_reserve(struct trace_buffer **current_rb, (trace_file->flags & (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) && (entry = this_cpu_read(trace_buffered_event))) { /* Try to use the per cpu buffer first */ + int max_len = PAGE_SIZE - struct_size(entry, array, 1); + val = this_cpu_inc_return(trace_buffered_event_cnt); - if ((len < (PAGE_SIZE - sizeof(*entry) - sizeof(entry->array[0]))) && val == 1) { + if (val == 1 && unlikely(len < max_len)) { trace_event_setup(entry, type, trace_ctx); entry->array[0] = len; return entry; -- 2.30.2