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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 63E94C10F14 for ; Thu, 10 Oct 2019 13:23:09 +0000 (UTC) Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 26B8920650 for ; Thu, 10 Oct 2019 13:23:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 26B8920650 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com Authentication-Results: mail.kernel.org; spf=fail smtp.mailfrom=kernelnewbies-bounces@kernelnewbies.org Received: from localhost ([::1] helo=shelob.surriel.com) by shelob.surriel.com with esmtp (Exim 4.92.3) (envelope-from ) id 1iIYOh-0006Ct-Gx; Thu, 10 Oct 2019 09:22:27 -0400 Received: from imladris.surriel.com ([96.67.55.152]) by shelob.surriel.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.3) (envelope-from ) id 1iIYOb-0006Cd-KU; Thu, 10 Oct 2019 09:22:21 -0400 Message-ID: Subject: Re: Software Prefetching using Machine learning From: Rik van Riel To: Irfan Ullah =?UTF-8?Q?=28=EC=9A=B8=EB=9D=BC_=EC=9D=B4=EB=A5=B4=ED=8C=90=29?= , Ruben Safir , valdis.kletnieks@vt.edu Date: Thu, 10 Oct 2019 09:22:21 -0400 In-Reply-To: References: <170918.1570648112@turing-police> User-Agent: Evolution 3.34.0 (3.34.0-1.fc31) MIME-Version: 1.0 Cc: greg@kroah.com, kernelnewbies@kernelnewbies.org X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============2672312011146376896==" Errors-To: kernelnewbies-bounces@kernelnewbies.org --===============2672312011146376896== Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-8lvlyjT4EW73aB7HAJ9W" --=-8lvlyjT4EW73aB7HAJ9W Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2019-10-10 at 11:10 +0900, Irfan Ullah (=EC=9A=B8=EB=9D=BC =EC=9D= =B4=EB=A5=B4=ED=8C=90) wrote: > Thank you for the responses. > It is not my assignment. Actually, we have initiated a project based > on the idea "incorporating artificial intelligence in the linux > kernel to increase its performance".=20 That is an interesting idea, but it is worth keeping in mind that most "kernel performance" is not about how well the kernel does something, but about how quickly the kernel lets userland programs do things. For example, I have done a lot of work on the scheduler code recently, and the most common thing I see (whenever I try something wrong) is for total CPU use in the system to go up. However, the increase in CPU time used is often in user space, and not in the kernel. For example, trying out a bad idea might result in 0.2% more CPU time spent in the kernel, but 2% more CPU time spent in user space, due to seeing a larger number of cache misses from user space programs. When things are done right, enabling a certain kernel feature might result in some overhead (say 0.3%), which is almost entirely caused by cache line misses, resulting in a total system overhead of twice that (0.6%), because every cache miss in my code results in something else getting evicted from the cache, and somebody else incurring a cache miss as well. In short, if you want to use machine learning to improve kernel performance, you need to figure out a way to do that without causing cache misses in any really hot path. That puts a serious constraint on what you can do. --=20 All Rights Reversed. --=-8lvlyjT4EW73aB7HAJ9W Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEKR73pCCtJ5Xj3yADznnekoTE3oMFAl2fMI0ACgkQznnekoTE 3oNdzQgAnRx41Zk6A+/t+YoECtQjOT4rquyO6URNMkgIlnjb52gwX5muIrxH5j+c xWqT4+hRrgDFQKDEyOQRPJai4HaqJynlfyFQnaA7zf8l+JA8GcNh4kaHlJ65oLHd dYkfJzJ9WCHa9eVAOOqMf4hPkdwSgWtCmfEUVmC1YeRYcBQexHyJHpAQRSw7nBKk 4wIvpsaSz2s8MnuDofM+HsBs4EVQF7eT5MrB7QnwRoPQf5k0q6zK1ceuzHN3bUPs WaVyu1Iif89HPi6mmFGZFrfKExAkabpk13AA6+E1g+epyWrA9m0tPAmOM9t1Ee56 q8ZzmRJXxgCg/L7U1VSU5jYnu+4oaA== =INB8 -----END PGP SIGNATURE----- --=-8lvlyjT4EW73aB7HAJ9W-- --===============2672312011146376896== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies --===============2672312011146376896==--