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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 1A13FC433E0 for ; Thu, 28 Jan 2021 15:05:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9E31564DFD for ; Thu, 28 Jan 2021 15:05:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9E31564DFD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E04A06B0070; Thu, 28 Jan 2021 10:05:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id DB5706B0072; Thu, 28 Jan 2021 10:05:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C56F36B0073; Thu, 28 Jan 2021 10:05:21 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0007.hostedemail.com [216.40.44.7]) by kanga.kvack.org (Postfix) with ESMTP id A94616B0070 for ; Thu, 28 Jan 2021 10:05:21 -0500 (EST) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 39CC8180AD837 for ; Thu, 28 Jan 2021 15:05:21 +0000 (UTC) X-FDA: 77755507242.30.A354460 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf01.hostedemail.com (Postfix) with ESMTP id 73B4B2007F5B for ; Thu, 28 Jan 2021 15:05:07 +0000 (UTC) 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> X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 73B4B2007F5B X-Stat-Signature: g5f43x5c6foyjg68gchoafmywqn5kn4n Received-SPF: none (infradead.org>: No applicable sender policy available) receiver=imf01; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1611846307-212852 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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?