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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 98CF1C432C0 for ; Fri, 29 Nov 2019 14:43:32 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 30C6C21736 for ; Fri, 29 Nov 2019 14:43:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 30C6C21736 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id F258F8854C; Fri, 29 Nov 2019 14:43:31 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id oKKVnKvCJ4db; Fri, 29 Nov 2019 14:43:31 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id 433F9883A6; Fri, 29 Nov 2019 14:43:31 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 3604CC1DD5; Fri, 29 Nov 2019 14:43:31 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 65E2EC0881 for ; Fri, 29 Nov 2019 14:43:29 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 4EDD1884D3 for ; Fri, 29 Nov 2019 14:43:29 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id P1GTE+2W25-f for ; Fri, 29 Nov 2019 14:43:28 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from huawei.com (lhrrgout.huawei.com [185.176.76.210]) by hemlock.osuosl.org (Postfix) with ESMTPS id C8D19883A6 for ; Fri, 29 Nov 2019 14:43:27 +0000 (UTC) Received: from LHREML711-CAH.china.huawei.com (unknown [172.18.7.107]) by Forcepoint Email with ESMTP id 18471A39C9AFC84A7EED; Fri, 29 Nov 2019 14:43:25 +0000 (GMT) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by LHREML711-CAH.china.huawei.com (10.201.108.34) with Microsoft SMTP Server (TLS) id 14.3.408.0; Fri, 29 Nov 2019 14:43:24 +0000 Received: from [127.0.0.1] (10.202.226.46) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Fri, 29 Nov 2019 14:43:24 +0000 Subject: Re: [Patch v2 1/3] iommu: match the original algorithm To: Cong Wang , References: <20191129004855.18506-1-xiyou.wangcong@gmail.com> <20191129004855.18506-2-xiyou.wangcong@gmail.com> From: John Garry Message-ID: Date: Fri, 29 Nov 2019 14:43:23 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20191129004855.18506-2-xiyou.wangcong@gmail.com> Content-Language: en-US X-Originating-IP: [10.202.226.46] X-ClientProxiedBy: lhreml720-chm.china.huawei.com (10.201.108.71) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Cc: linux-kernel@vger.kernel.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 29/11/2019 00:48, Cong Wang wrote: > The IOVA cache algorithm implemented in IOMMU code does not > exactly match the original algorithm described in the paper. > which paper? > Particularly, it doesn't need to free the loaded empty magazine > when trying to put it back to global depot. To make it work, we > have to pre-allocate magazines in the depot and only recycle them > when all of them are full. > > Before this patch, rcache->depot[] contains either full or > freed entries, after this patch, it contains either full or > empty (but allocated) entries. I *quickly* tested this patch and got a small performance gain. > > Cc: Joerg Roedel > Signed-off-by: Cong Wang > --- > drivers/iommu/iova.c | 45 +++++++++++++++++++++++++++----------------- > 1 file changed, 28 insertions(+), 17 deletions(-) > > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c > index 41c605b0058f..cb473ddce4cf 100644 > --- a/drivers/iommu/iova.c > +++ b/drivers/iommu/iova.c > @@ -862,12 +862,16 @@ static void init_iova_rcaches(struct iova_domain *iovad) > struct iova_cpu_rcache *cpu_rcache; > struct iova_rcache *rcache; > unsigned int cpu; > - int i; > + int i, j; > > for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) { > rcache = &iovad->rcaches[i]; > spin_lock_init(&rcache->lock); > rcache->depot_size = 0; > + for (j = 0; j < MAX_GLOBAL_MAGS; ++j) { > + rcache->depot[j] = iova_magazine_alloc(GFP_KERNEL); > + WARN_ON(!rcache->depot[j]); > + } > rcache->cpu_rcaches = __alloc_percpu(sizeof(*cpu_rcache), cache_line_size()); > if (WARN_ON(!rcache->cpu_rcaches)) > continue; > @@ -900,24 +904,30 @@ static bool __iova_rcache_insert(struct iova_domain *iovad, > > if (!iova_magazine_full(cpu_rcache->loaded)) { > can_insert = true; > - } else if (!iova_magazine_full(cpu_rcache->prev)) { > + } else if (iova_magazine_empty(cpu_rcache->prev)) { is this change strictly necessary? > swap(cpu_rcache->prev, cpu_rcache->loaded); > can_insert = true; > } else { > - struct iova_magazine *new_mag = iova_magazine_alloc(GFP_ATOMIC); > + spin_lock(&rcache->lock); > + if (rcache->depot_size < MAX_GLOBAL_MAGS) { > + swap(rcache->depot[rcache->depot_size], cpu_rcache->prev); > + swap(cpu_rcache->prev, cpu_rcache->loaded); > + rcache->depot_size++; > + can_insert = true; > + } else { > + mag_to_free = cpu_rcache->loaded; > + } > + spin_unlock(&rcache->lock); > + > + if (mag_to_free) { > + struct iova_magazine *new_mag = iova_magazine_alloc(GFP_ATOMIC); > > - if (new_mag) { > - spin_lock(&rcache->lock); > - if (rcache->depot_size < MAX_GLOBAL_MAGS) { > - rcache->depot[rcache->depot_size++] = > - cpu_rcache->loaded; > + if (new_mag) { > + cpu_rcache->loaded = new_mag; > + can_insert = true; > } else { > - mag_to_free = cpu_rcache->loaded; > + mag_to_free = NULL; > } > - spin_unlock(&rcache->lock); > - > - cpu_rcache->loaded = new_mag; > - can_insert = true; > } > } > > @@ -963,14 +973,15 @@ static unsigned long __iova_rcache_get(struct iova_rcache *rcache, > > if (!iova_magazine_empty(cpu_rcache->loaded)) { > has_pfn = true; > - } else if (!iova_magazine_empty(cpu_rcache->prev)) { > + } else if (iova_magazine_full(cpu_rcache->prev)) { > swap(cpu_rcache->prev, cpu_rcache->loaded); > has_pfn = true; > } else { > spin_lock(&rcache->lock); > if (rcache->depot_size > 0) { > - iova_magazine_free(cpu_rcache->loaded); it is good to remove this from under the lock, apart from this change > - cpu_rcache->loaded = rcache->depot[--rcache->depot_size]; > + swap(rcache->depot[rcache->depot_size - 1], cpu_rcache->prev); > + swap(cpu_rcache->prev, cpu_rcache->loaded); > + rcache->depot_size--; I'm not sure how appropriate the name "depot_size" is any longer. > has_pfn = true; > } > spin_unlock(&rcache->lock); > @@ -1019,7 +1030,7 @@ static void free_iova_rcaches(struct iova_domain *iovad) > iova_magazine_free(cpu_rcache->prev); > } > free_percpu(rcache->cpu_rcaches); > - for (j = 0; j < rcache->depot_size; ++j) > + for (j = 0; j < MAX_GLOBAL_MAGS; ++j) > iova_magazine_free(rcache->depot[j]); > } > } > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu