From patchwork Sat Sep 7 17:25:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 11136575 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 440681708 for ; Sat, 7 Sep 2019 17:25:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 19A3F208C3 for ; Sat, 7 Sep 2019 17:25:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="YVxuP3Qw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392981AbfIGRZR (ORCPT ); Sat, 7 Sep 2019 13:25:17 -0400 Received: from mail-oi1-f194.google.com ([209.85.167.194]:33230 "EHLO mail-oi1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392548AbfIGRZR (ORCPT ); Sat, 7 Sep 2019 13:25:17 -0400 Received: by mail-oi1-f194.google.com with SMTP id e12so7303887oie.0; Sat, 07 Sep 2019 10:25:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:from:to:cc:date:message-id:in-reply-to:references :user-agent:mime-version:content-transfer-encoding; bh=rtCJ9oXMvzyqzSO/6+XMP8VFA+c1bypJ2A9Wi4tC2B0=; b=YVxuP3Qw60ve+K16OV/2OTXTVXsnZSGiw8yXWOnvCSAPW2RJsbvv9esY2jbVJk+MTd gZaFZgeUDSH31cxpn+4ACT+RtrLyEzlpB9CSFSKqcLbBdu5k7zv4t9ddGWWi0TGCGwiu gFWbCI/pIFOqwAWmWO0aBRiIEO3n1vCRrqraKqGz8fVFzLWJMKaeT4nkP76nJ9dVqS5M mGxpfLI0pp+7NdvVFdGAITNx/Whl+E8KWWUR6DpIaXjDSmYY2Hh+szZWNaDpLgznhs4Y DGw/CpIO4ALtMzKoFiREaJMW+0Vo1vWKa+L+gYpEaIJGJWvuU4XIhs/WSIDDM2sUHuCP a9dA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:date:message-id:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=rtCJ9oXMvzyqzSO/6+XMP8VFA+c1bypJ2A9Wi4tC2B0=; b=PS58XQ9jAcbwuo3QBBoNSSqjFVMN5GvkdpuoMRdREfxkyF8OTHmBdVwfuMsPxYVaKT 8jqf7lwzxeIOEiNexjLIcBPZct0lRPrVd0qJgSoSE92/pfFXGWufgxwqunRzjro++XZ3 3Gaitecd9vfXwlgASMG71ho74sltMbOF4dXVHp/OoE+ghNQ/njxuzC8SNAs8cnFaIcME NzS2Qt0Dm+hJiGyNDyB/JenNZbKy3/9Ofh3RZeGfyCO/NA87sZfxaxYsM2/H8Ar0IPhd dhDnq04e3yJOnXkffN/QSCxB/ZUghXJRA3foaTL+Bi1VmyFTNvKv8pq9BcSsH6JfffHx 1o6A== X-Gm-Message-State: APjAAAVBjfhwC/t8yUNeWFuYe1DWTzplf0PJFBSmHYmpvljuLCc4S52O Nko6g0LtcvL8E11PGMsBQrk= X-Google-Smtp-Source: APXvYqx76pbWI8aVf7Yn3gxH+LEAS1HoAzYWQhYG1OYCBkmvO+49isQhgNq9dB292v9n9IEZQlObWg== X-Received: by 2002:aca:b388:: with SMTP id c130mr12021078oif.27.1567877115467; Sat, 07 Sep 2019 10:25:15 -0700 (PDT) Received: from localhost.localdomain ([2001:470:b:9c3:9e5c:8eff:fe4f:f2d0]) by smtp.gmail.com with ESMTPSA id h5sm3898728oth.29.2019.09.07.10.25.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 07 Sep 2019 10:25:15 -0700 (PDT) Subject: [PATCH v9 1/8] mm: Add per-cpu logic to page shuffling From: Alexander Duyck To: virtio-dev@lists.oasis-open.org, kvm@vger.kernel.org, mst@redhat.com, catalin.marinas@arm.com, david@redhat.com, dave.hansen@intel.com, linux-kernel@vger.kernel.org, willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, will@kernel.org, linux-arm-kernel@lists.infradead.org, osalvador@suse.de Cc: yang.zhang.wz@gmail.com, pagupta@redhat.com, konrad.wilk@oracle.com, nitesh@redhat.com, riel@surriel.com, lcapitulino@redhat.com, wei.w.wang@intel.com, aarcange@redhat.com, ying.huang@intel.com, pbonzini@redhat.com, dan.j.williams@intel.com, fengguang.wu@intel.com, alexander.h.duyck@linux.intel.com, kirill.shutemov@linux.intel.com Date: Sat, 07 Sep 2019 10:25:12 -0700 Message-ID: <20190907172512.10910.74435.stgit@localhost.localdomain> In-Reply-To: <20190907172225.10910.34302.stgit@localhost.localdomain> References: <20190907172225.10910.34302.stgit@localhost.localdomain> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Alexander Duyck Change the logic used to generate randomness in the suffle path so that we can avoid cache line bouncing. The previous logic was sharing the offset and entropy word between all CPUs. As such this can result in cache line bouncing and will ultimately hurt performance when enabled. To resolve this I have moved to a per-cpu logic for maintaining a unsigned long containing some amount of bits, and an offset value for which bit we can use for entropy with each call. Reviewed-by: Dan Williams Signed-off-by: Alexander Duyck --- mm/shuffle.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/mm/shuffle.c b/mm/shuffle.c index 3ce12481b1dc..9ba542ecf335 100644 --- a/mm/shuffle.c +++ b/mm/shuffle.c @@ -183,25 +183,38 @@ void __meminit __shuffle_free_memory(pg_data_t *pgdat) shuffle_zone(z); } +struct batched_bit_entropy { + unsigned long entropy_bool; + int position; +}; + +static DEFINE_PER_CPU(struct batched_bit_entropy, batched_entropy_bool); + void add_to_free_area_random(struct page *page, struct free_area *area, int migratetype) { - static u64 rand; - static u8 rand_bits; + struct batched_bit_entropy *batch; + unsigned long entropy; + int position; /* - * The lack of locking is deliberate. If 2 threads race to - * update the rand state it just adds to the entropy. + * We shouldn't need to disable IRQs as the only caller is + * __free_one_page and it should only be called with the zone lock + * held and either from IRQ context or with local IRQs disabled. */ - if (rand_bits == 0) { - rand_bits = 64; - rand = get_random_u64(); + batch = raw_cpu_ptr(&batched_entropy_bool); + position = batch->position; + + if (--position < 0) { + batch->entropy_bool = get_random_long(); + position = BITS_PER_LONG - 1; } - if (rand & 1) + batch->position = position; + entropy = batch->entropy_bool; + + if (1ul & (entropy >> position)) add_to_free_area(page, area, migratetype); else add_to_free_area_tail(page, area, migratetype); - rand_bits--; - rand >>= 1; }