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=-3.7 required=3.0 tests=BAYES_00, 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 9F9D1C4363D for ; Fri, 2 Oct 2020 13:53:15 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1F39E206C3 for ; Fri, 2 Oct 2020 13:53:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F39E206C3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6472B6B005D; Fri, 2 Oct 2020 09:53:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5D1DE6B0068; Fri, 2 Oct 2020 09:53:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4C0B66B006C; Fri, 2 Oct 2020 09:53:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0129.hostedemail.com [216.40.44.129]) by kanga.kvack.org (Postfix) with ESMTP id 1BF276B005D for ; Fri, 2 Oct 2020 09:53:10 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B2A458249980 for ; Fri, 2 Oct 2020 13:53:09 +0000 (UTC) X-FDA: 77327126898.10.trip54_21022db271a4 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin10.hostedemail.com (Postfix) with ESMTP id 874C916A0DE for ; Fri, 2 Oct 2020 13:53:09 +0000 (UTC) X-HE-Tag: trip54_21022db271a4 X-Filterd-Recvd-Size: 3966 Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Fri, 2 Oct 2020 13:53:09 +0000 (UTC) Received: from imladris.surriel.com ([96.67.55.152]) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1kOLUf-0007D4-LO; Fri, 02 Oct 2020 09:53:05 -0400 Message-ID: <656725362af9bd757a281f0799a0bb9c9b2487bd.camel@surriel.com> Subject: Re: [RFC PATCH 1/1] vmscan: Support multiple kswapd threads per node From: Rik van Riel To: Michal Hocko , Sebastiaan Meijer Cc: akpm@linux-foundation.org, buddy.lumpkin@oracle.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mgorman@suse.de, willy@infradead.org Date: Fri, 02 Oct 2020 09:53:05 -0400 In-Reply-To: <20201002070333.GA21871@dhcp22.suse.cz> References: <20201001123032.GC22560@dhcp22.suse.cz> <20201002070333.GA21871@dhcp22.suse.cz> Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-BFY58aSTZaJWRrNfOho7" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 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: --=-BFY58aSTZaJWRrNfOho7 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2020-10-02 at 09:03 +0200, Michal Hocko wrote: > On Thu 01-10-20 18:18:10, Sebastiaan Meijer wrote: > > (Apologies for messing up the mailing list thread, Gmail had fooled > > me into > > believing that it properly picked up the thread) > >=20 > > On Thu, 1 Oct 2020 at 14:30, Michal Hocko wrote: > > > On Wed 30-09-20 21:27:12, Sebastiaan Meijer wrote: > > > > > yes it shows the bottleneck but it is quite artificial. Read > > > > > data is > > > > > usually processed and/or written back and that changes the > > > > > picture a > > > > > lot. > > > > Apologies for reviving an ancient thread (and apologies in > > > > advance for my lack > > > > of knowledge on how mailing lists work), but I'd like to offer > > > > up another > > > > reason why merging this might be a good idea. > > > >=20 > > > > From what I understand, zswap runs its compression on the same > > > > kswapd thread, > > > > limiting it to a single thread for compression. Given enough > > > > processing power, > > > > zswap can get great throughput using heavier compression > > > > algorithms like zstd, > > > > but this is currently greatly limited by the lack of threading. > > >=20 > > > Isn't this a problem of the zswap implementation rather than > > > general > > > kswapd reclaim? Why zswap doesn't do the same as normal swap out > > > in a > > > context outside of the reclaim? On systems with lots of very fast IO devices, we have also seen kswapd take 100% CPU time without any zswap in use. This seems like a generic issue, though zswap does manage to bring it out on lower end systems. --=20 All Rights Reversed. --=-BFY58aSTZaJWRrNfOho7 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEKR73pCCtJ5Xj3yADznnekoTE3oMFAl93MMEACgkQznnekoTE 3oM2fgf/QtTnRf6iTyspPZhRqxZnXaDD8urYvTIfEZQeun7dIZsjsY7hO1GE+kLl XI0X40UGXcCHbgi+YFxAjjoqsf2zRLK2mnzIyU/9baXolq+tepDEtSNZ+2qiCtAF Muw+BEEU6680aP5AFl0RYvsO8WwbnmGfeTslLsJNf9ZJMCs4AYlaS9tairWMhXGw ZUyoLjz8tJywNUc3gufu65KNE1nIXNHyxKVeEFJmBzEobRmiVLG1c3Fsz+cTC2Ue zqaIZpAqS1H7RL3u/E01oSHhd6mDDc/PdDRkpcuyfuKdL5EGUuyoXzNhGEARvt4Z 4UkK0E03+bjtnKtyAkKqZ3KDh6h45g== =hVUa -----END PGP SIGNATURE----- --=-BFY58aSTZaJWRrNfOho7--