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=-5.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,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 539F1C4727C for ; Tue, 22 Sep 2020 17:12:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id ADE562399A for ; Tue, 22 Sep 2020 17:12:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="ujHrSPNv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ADE562399A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C938C90000A; Tue, 22 Sep 2020 13:12:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C1F20900002; Tue, 22 Sep 2020 13:12:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B35E990000A; Tue, 22 Sep 2020 13:12:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0222.hostedemail.com [216.40.44.222]) by kanga.kvack.org (Postfix) with ESMTP id 9EC45900002 for ; Tue, 22 Sep 2020 13:12:53 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 5D5DB1EF1 for ; Tue, 22 Sep 2020 17:12:53 +0000 (UTC) X-FDA: 77291342226.22.cent38_2e0c3012714f Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin22.hostedemail.com (Postfix) with ESMTP id 39D7C18038E67 for ; Tue, 22 Sep 2020 17:12:53 +0000 (UTC) X-HE-Tag: cent38_2e0c3012714f X-Filterd-Recvd-Size: 2041 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf16.hostedemail.com (Postfix) with ESMTP for ; Tue, 22 Sep 2020 17:12:52 +0000 (UTC) Received: from X1 (unknown [216.241.194.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4B8112084C; Tue, 22 Sep 2020 17:12:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600794771; bh=eZGm04xbBcFoJWyknH6yEKYWUp0W5WKKh0BhzYdfN0s=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ujHrSPNvT6frdqxXRUSFbCDbEYWHSgeXd4mZCrAJvOCqgPy/ok+gMbPdYsEjcfUGs AR9vOobIPlXSLaoqmovvp/dzRoLVkrf2N+YcCn2NzjzI2ikqYOc5ZqZHdnRrnn4d4A oU6P2HWdSHPr2a8GIdPHU37i5rnOgDvSqZQvT8Q8= Date: Tue, 22 Sep 2020 10:12:50 -0700 From: Andrew Morton To: Rik van Riel Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@fb.com, niketa@fb.com, sjenning@redhat.com, ddstreet@ieee.org, konrad.wilk@oracle.com, hannes@cmpxchg.org Subject: Re: [PATCH 0/2] mm,swap: skip swap readahead for instant IO (like zswap) Message-Id: <20200922101250.527d9e676fefbb4c8d0cd5b9@linux-foundation.org> In-Reply-To: <20200922020148.3261797-1-riel@surriel.com> References: <20200922020148.3261797-1-riel@surriel.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Mon, 21 Sep 2020 22:01:46 -0400 Rik van Riel wrote: > Both with frontswap/zswap, and with some extremely fast IO devices, > swap IO will be done before the "asynchronous" swap_readpage() call > has returned. > > In that case, doing swap readahead only wastes memory, increases > latency, and increases the chances of needing to evict something more > useful from memory. In that case, just skip swap readahead. Any quantitative testing results?