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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B644FC43334 for ; Thu, 14 Jul 2022 19:58:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240083AbiGNT6K (ORCPT ); Thu, 14 Jul 2022 15:58:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53504 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232355AbiGNT6I (ORCPT ); Thu, 14 Jul 2022 15:58:08 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 21CFD57210; Thu, 14 Jul 2022 12:58:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=B2jr/3frCctEW27dermWNQ8i6KyhP3JVqMfQDwDHZjA=; b=hVEJYr2zXRgYx3w9ib5XzoVw7E ZV2JiN5sj/13QkpVpG/ACognSo+jlqrTarcO1tRkTrzOUsQPB1oF6O6l99lS0E0mSqlgA22KCmgGS Q4VyJELFwkzbFSPFWSM7dVwIMPuwFEz4LzcMINsHrBlLazs2MfdaMVqN/bVdlnBZKyzvMEmFNV7pj galy+XGL2wdd1o5PTwGKusUYLLaksZTB9F+s5jTVZiRSP1EEl0p3rBdLTYiW7pUhwpKABHFW/sipu H73e6Te3KaWCVf1FGd4mPYUqQRV5xhpXc6uxSgAsnwblVlN+CVpQr/ZoNosj7leAnjEUFZ8i2z05E 8LY8HkkA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1oC4y6-009duX-5C; Thu, 14 Jul 2022 19:57:50 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id DB2F1980185; Thu, 14 Jul 2022 21:57:48 +0200 (CEST) Date: Thu, 14 Jul 2022 21:57:48 +0200 From: Peter Zijlstra To: Dmitrii Dolgov <9erthalion6@gmail.com> Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, songliubraving@fb.com, rostedt@goodmis.org, mingo@redhat.com, mhiramat@kernel.org, alexei.starovoitov@gmail.com Subject: Re: [PATCH v4 1/1] perf/kprobe: maxactive for fd-based kprobe Message-ID: References: <20220714193403.13211-1-9erthalion6@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220714193403.13211-1-9erthalion6@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 14, 2022 at 09:34:03PM +0200, Dmitrii Dolgov wrote: > From: Song Liu > > Enable specifying maxactive for fd based kretprobe. This will be useful > for tracing tools like bcc and bpftrace (see for example discussion [1]). > Use highest 4 bit (bit 59-63) to allow specifying maxactive by log2. What's maxactive? This doesn't really tell me much. Why are the top 4 bits the best to use? > > The original patch [2] seems to be fallen through the cracks and wasn't > applied. I've merely rebased the work done by Song Liu, verififed it > still works, and modified to allow specifying maxactive by log2 per > suggestion from the discussion thread. That just doesn't belong in a Changelog. > > Note that changes in rethook implementation may render maxactive > obsolete. Then why bother creating an ABI for it? > > [1]: https://github.com/iovisor/bpftrace/issues/835 > [2]: https://lore.kernel.org/all/20191007223111.1142454-1-songliubraving@fb.com/ > > Signed-off-by: Song Liu > Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com> > Reviewed-by: Masami Hiramatsu (Google) > Acked-by: Steven Rostedt (Google) Lots of question and not a single answer in sight...