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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham 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 60877C432C3 for ; Fri, 15 Nov 2019 22:57:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 35A2320733 for ; Fri, 15 Nov 2019 22:57:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="OgszDbwy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727064AbfKOW5U (ORCPT ); Fri, 15 Nov 2019 17:57:20 -0500 Received: from mail-vs1-f74.google.com ([209.85.217.74]:38549 "EHLO mail-vs1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726973AbfKOW5T (ORCPT ); Fri, 15 Nov 2019 17:57:19 -0500 Received: by mail-vs1-f74.google.com with SMTP id b63so1724373vsb.5 for ; Fri, 15 Nov 2019 14:57:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=053BG20b593X/SMWxmhUI3JuwfglYUEj/JJwvN0h+wU=; b=OgszDbwyMvl11IRddPSG1mPf/uKCmY4IqAIBsD9+gVpRRzbJNw/mGNYvXxiVPrFVlW Aan5NICVu021n+/8xCWhTuE9mSOagqWWylR2U1uKY8N0c85LOHRC1nUM/upCmSciUrMm L3fXvrx1Uk2QZW3t0IA3VZMFUloVadHsmDDW+KPK4k4GT7VKWyNZdrh8ttIgPHliRJeX oQcAUGnn+otpz+RosyXPRGtGt4m+DI5iIbRw8uYGN1wbpdHiKugQcL14vgh+MrAYrh+Q O5rLxF4hJC6r+aDPdWf2qGbrnRjt4jg41pNONTu21HGtbs4rq2MKcszV50lWWRTdmALY fagw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=053BG20b593X/SMWxmhUI3JuwfglYUEj/JJwvN0h+wU=; b=rJpEC/OSMnCFf8f2hoI71lGouirp7OUQ4uO6yZQPBfuXCwItChX/svbD9b2UJ2r8w5 2D8HrtbTvujVYIfKzkjwfMaCg597BLirYpkEev5uQ2IwP5tYp2f9HyyD6xQmuWCb+E9M lNzlLLsPOYCOqIqfTyTU7V3vG/6zqum5rZEQGLTqgAszyEPvQkKkYxuE/v82nn6HwniS +hCGjLDxuLmckBe6XD+NP9Ol/USM6CadKJmqnT2f9o4ZmOXRGrBb0wYH8FswKmic7Z7v xAAluXh0kThGUHiEYJ8jl48N9HTWHAEuJakP2io70DClLz2jxqYBdi63226G6J9xUXxK 4T8g== X-Gm-Message-State: APjAAAV74+Bo++LAsmzzztFpKeMxIrar/MxGYJ3ElIPQcAVpfCFConil kzYI76iNlANHOflnd1WtaVkmpqr+us8= X-Google-Smtp-Source: APXvYqx3wRvRkGdHuMten4uCTPE1JRvBvAHB9IpdCd+K6gFc9krOXqH3S+Xlx6k/0TTMaKJM1vLZB3+1a2w= X-Received: by 2002:a67:c995:: with SMTP id y21mr2878122vsk.158.1573858638823; Fri, 15 Nov 2019 14:57:18 -0800 (PST) Date: Fri, 15 Nov 2019 14:55:57 -0800 Message-Id: <20191115225557.61847-1-khazhy@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.24.0.432.g9d3f5f5b63-goog Subject: [PATCH] virtio_balloon: fix shrinker pages_to_free calculation From: Khazhismel Kumykov To: mst@redhat.com, jasowang@redhat.com, wei.w.wang@intel.com Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Khazhismel Kumykov Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org To my reading, we're accumulating total freed pages in pages_freed, but subtracting it every iteration from pages_to_free, meaning we'll count earlier iterations multiple times, freeing fewer pages than expected. Just accumulate in pages_freed, and compare to pages_to_free. There's also a unit mismatch, where pages_to_free seems to be virtio balloon pages, and pages_freed is system pages (We divide by VIRTIO_BALLOON_PAGES_PER_PAGE), so sutracting pages_freed from pages_to_free may result in freeing too much. There also seems to be a mismatch between shrink_free_pages() and shrink_balloon_pages(), where in both pages_to_free is given as # of virtio pages to free, but free_pages() returns virtio pages, and balloon_pages returns system pages. (For 4K PAGE_SIZE, this mismatch wouldn't be noticed since VIRTIO_BALLOON_PAGES_PER_PAGE would be 1) Have both return virtio pages, and divide into system pages when returning from shrinker_scan() Fixes: 71994620bb25 ("virtio_balloon: replace oom notifier with shrinker") Cc: Wei Wang Signed-off-by: Khazhismel Kumykov --- Tested this under memory pressure conditions and the shrinker seemed to shrink. drivers/virtio/virtio_balloon.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 226fbb995fb0..7951ece3fe24 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -782,11 +782,8 @@ static unsigned long shrink_balloon_pages(struct virtio_balloon *vb, * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it * multiple times to deflate pages till reaching pages_to_free. */ - while (vb->num_pages && pages_to_free) { - pages_freed += leak_balloon(vb, pages_to_free) / - VIRTIO_BALLOON_PAGES_PER_PAGE; - pages_to_free -= pages_freed; - } + while (vb->num_pages && pages_to_free > pages_freed) + pages_freed += leak_balloon(vb, pages_to_free - pages_freed); update_balloon_size(vb); return pages_freed; @@ -805,11 +802,11 @@ static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker, pages_freed = shrink_free_pages(vb, pages_to_free); if (pages_freed >= pages_to_free) - return pages_freed; + return pages_freed / VIRTIO_BALLOON_PAGES_PER_PAGE; pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed); - return pages_freed; + return pages_freed / VIRTIO_BALLOON_PAGES_PER_PAGE; } static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker, -- 2.24.0.432.g9d3f5f5b63-goog