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=-0.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, 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 5CB0FC2D0C6 for ; Wed, 11 Dec 2019 21:04:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3097421556 for ; Wed, 11 Dec 2019 21:04:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cmpxchg-org.20150623.gappssmtp.com header.i=@cmpxchg-org.20150623.gappssmtp.com header.b="ns0LNqCK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726463AbfLKVEE (ORCPT ); Wed, 11 Dec 2019 16:04:04 -0500 Received: from mail-qv1-f68.google.com ([209.85.219.68]:39973 "EHLO mail-qv1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726313AbfLKVEE (ORCPT ); Wed, 11 Dec 2019 16:04:04 -0500 Received: by mail-qv1-f68.google.com with SMTP id k10so39696qve.7 for ; Wed, 11 Dec 2019 13:04:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=R2PsJGyUpT/iCCg3Yu1TE62l+3HqSX40NgPM4bJnXXE=; b=ns0LNqCK0sYLbEaXEgQbTfsQKmSRApUdDpdU2giNA2frUZuVy2AITBGjQhQCZ5XAa0 OHf1XkkRoh7S2lLFqDTDbkqwjISEBUfNG24iQrcfZZ1haypZdUbUWHPjIxpK/bkmMBep B4hRCgqs/F0xu5pP7Gg7dF4ox3R0hHZIzlLeI9dfHw1fXzvWshQvz/0yNkyv/pvgKa9P q0uHYaraQXOIRT5ZpD26hDr+If9EUKfw1sBVqVMHKNM+6OmHzWl7vfyZfrbAAA0iPFVF aIHDbRd/baN0rTREQXjK3D4I2V3SvB/4naasUMiqpOrxucdePn9SUxooXkbrbtKXECHz JI+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=R2PsJGyUpT/iCCg3Yu1TE62l+3HqSX40NgPM4bJnXXE=; b=B9F9cTNkK80cb9oURurCWDvHlBFHx51tXK/WWW6ucwTx/3/Fu6G8X0hs+/izT22jpU N5rQ2fk6G8OZAhuj84j0QgjRRjTJxvHU5aGN8LQFNm07ehQoyZ9G/B5fS5BJaJ6wn7dT 0OYWzcts0odMU4CvUb/B2YwuwEl8X9gOFY+gn6b9B50iFUQB+Ev/k0l1AnqG77SESuvo XEne0RfLVIoPZWrFD7ixx3B+r/3e55CqWvnV1ugCTGtjFd1a+yQKf18tA3hHG7nMPLtG Lqq5EgtAwqLzCDUTe3ttRzpRGz5y1xcXMuJnGfLNCoEmwOniHLQzKXRG96Rx3a1l9M5S 7a2A== X-Gm-Message-State: APjAAAX2lnHqyp94jSu6hjHYQHSV4JXoRU1OCIs2EsSDLsQCxUgtY+ic I4p5E1iJ9WMSLG3CTVFy37owaw== X-Google-Smtp-Source: APXvYqxq7v6drlnORg/gNcxlU4z0/vNmm+oh4UJTRbqnR5xBG4N1pG1N3WEFTCGN7D9u37ud9MdVmg== X-Received: by 2002:a0c:e14f:: with SMTP id c15mr4886674qvl.169.1576098243448; Wed, 11 Dec 2019 13:04:03 -0800 (PST) Received: from localhost ([2620:10d:c091:500::151b]) by smtp.gmail.com with ESMTPSA id h34sm1307215qtc.62.2019.12.11.13.04.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Dec 2019 13:04:02 -0800 (PST) Date: Wed, 11 Dec 2019 16:04:01 -0500 From: Johannes Weiner To: Linus Torvalds Cc: Jens Axboe , Linux-MM , linux-fsdevel , linux-block , Matthew Wilcox , Chris Mason , Dave Chinner Subject: Re: [PATCHSET v3 0/5] Support for RWF_UNCACHED Message-ID: <20191211210401.GA158617@cmpxchg.org> References: <20191211152943.2933-1-axboe@kernel.dk> <0d4e3954-c467-30a7-5a8e-7c4180275533@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Dec 11, 2019 at 12:18:38PM -0800, Linus Torvalds wrote: > On Wed, Dec 11, 2019 at 12:08 PM Jens Axboe wrote: > > > > $ cat /proc/meminfo | grep -i active > > Active: 134136 kB > > Inactive: 28683916 kB > > Active(anon): 97064 kB > > Inactive(anon): 4 kB > > Active(file): 37072 kB > > Inactive(file): 28683912 kB > > Yeah, that should not put pressure on some swap activity. We have 28 > GB of basically free inactive file data, and the VM is doing something > very very bad if it then doesn't just quickly free it with no real > drama. I was looking at this with Jens offline last week. One thing to note is the rate of IO that Jens is working with: combined with the low cache hit rate, it was pushing upwards of half a million pages through the page cache each second. There isn't anything obvious sticking out in the kswapd profile: it's dominated by cache tree deletions (or rather replacing pages with shadow entries, hence the misleading xas_store()), tree lock contention, etc. - all work that a direct reclaimer would have to do as well, with one exceptions: RWC_UNCACHED doesn't need to go through the LRU list, and 8-9% of kswapd cycles alone are going into physically getting pages off the list. (And I suspect part of that is also contention over the LRU lock as kswapd gets overwhelmed and direct reclaim kicks in). Jens, how much throughput difference does kswapd vs RWC_UNCACHED make?