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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 DC431C433E9 for ; Thu, 28 Jan 2021 15:06:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9AA4E64DFB for ; Thu, 28 Jan 2021 15:06:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232473AbhA1PG1 (ORCPT ); Thu, 28 Jan 2021 10:06:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231696AbhA1PFl (ORCPT ); Thu, 28 Jan 2021 10:05:41 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3C33C061574; Thu, 28 Jan 2021 07:05:00 -0800 (PST) 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=i2BpbjiEMy/uoZsV+pGyxXHIRXV75JS+gpJXaA6/Vt8=; b=uVQQCvvuifCvUNXxKzqoRVkwCg EsPu11izlSdVbGdWwh4F+y57Z2DPUgDJPXg3NePMa092xK+QeqQ8ov3tLWJeJbnRIVVHScPtdd/dB pNEhjfVmx5qzUx9y50jFU84q0vf1eY8GW9YXZJ9bzbIJQSVkMrYysBXdjCpurDVoGURqNuM2KSHRD NLZRZHr37qIy2UirH5j+biqJRZ/zAYA5zpbVQQWueuvy+d7nNSk7vjeGD3ysYBq78+XMM5BfovMfn vPcQV29IHOWLJIYfgbg4wS13zfzu0RSCjGAWfmXQ73wo2pRbHS09QjG8NW+gbzIFn3kwqII4h6mnf vpl+50Kg==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1l58qi-008bRt-3T; Thu, 28 Jan 2021 15:04:48 +0000 Date: Thu, 28 Jan 2021 15:04:44 +0000 From: Matthew Wilcox To: Saravanan D Cc: x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, corbet@lwn.net, linux-kernel@vger.kernel.org, kernel-team@fb.com, linux-doc@vger.kernel.org, linux-mm@kvack.org, songliubraving@fb.com Subject: Re: [PATCH V5] x86/mm: Tracking linear mapping split events Message-ID: <20210128150444.GY308988@casper.infradead.org> References: <20210128045153.GW308988@casper.infradead.org> <20210128104934.2916679-1-saravanand@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210128104934.2916679-1-saravanand@fb.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 28, 2021 at 02:49:34AM -0800, Saravanan D wrote: > One of the many lasting (as we don't coalesce back) sources for huge page > splits is tracing as the granular page attribute/permission changes would > force the kernel to split code segments mapped to huge pages to smaller > ones thereby increasing the probability of TLB miss/reload even after > tracing has been stopped. You didn't answer my question. Is this tracing of userspace programs causing splits, or is it kernel tracing? Also, we have lots of kinds of tracing these days; are you referring to kprobes? tracepoints? ftrace? Something else?