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=-13.1 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 44DE0C43464 for ; Fri, 18 Sep 2020 14:18:17 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (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 C30B221582 for ; Fri, 18 Sep 2020 14:18:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C30B221582 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.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 silver.osuosl.org (Postfix) with ESMTP id 72C352E201; Fri, 18 Sep 2020 14:18:16 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id LM+rVoDPWPQM; Fri, 18 Sep 2020 14:18:13 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by silver.osuosl.org (Postfix) with ESMTP id 942CF2E20F; Fri, 18 Sep 2020 14:18:13 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 6607BC0888; Fri, 18 Sep 2020 14:18:13 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 854E9C0051 for ; Fri, 18 Sep 2020 14:18:11 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 710A3876BF for ; Fri, 18 Sep 2020 14:18:11 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id BOJTwKopPYRP for ; Fri, 18 Sep 2020 14:18:10 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by whitealder.osuosl.org (Postfix) with ESMTP id 316C7876FB for ; Fri, 18 Sep 2020 14:18:10 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 77AFA1045; Fri, 18 Sep 2020 07:18:09 -0700 (PDT) Received: from [10.57.47.84] (unknown [10.57.47.84]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 222273F718; Fri, 18 Sep 2020 07:18:05 -0700 (PDT) Subject: Re: [PATCH v2 1/2] iommu/iova: Retry from last rb tree node if iova search fails To: vjitta@codeaurora.org, joro@8bytes.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <1597927761-24441-1-git-send-email-vjitta@codeaurora.org> From: Robin Murphy Message-ID: <07270e29-c9d4-ae8c-a236-eb6fefccbf6c@arm.com> Date: Fri, 18 Sep 2020 15:18:04 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 MIME-Version: 1.0 In-Reply-To: <1597927761-24441-1-git-send-email-vjitta@codeaurora.org> Content-Language: en-GB Cc: vinmenon@codeaurora.org, kernel-team@android.com 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 2020-08-20 13:49, vjitta@codeaurora.org wrote: > From: Vijayanand Jitta > > When ever a new iova alloc request comes iova is always searched > from the cached node and the nodes which are previous to cached > node. So, even if there is free iova space available in the nodes > which are next to the cached node iova allocation can still fail > because of this approach. > > Consider the following sequence of iova alloc and frees on > 1GB of iova space > > 1) alloc - 500MB > 2) alloc - 12MB > 3) alloc - 499MB > 4) free - 12MB which was allocated in step 2 > 5) alloc - 13MB > > After the above sequence we will have 12MB of free iova space and > cached node will be pointing to the iova pfn of last alloc of 13MB > which will be the lowest iova pfn of that iova space. Now if we get an > alloc request of 2MB we just search from cached node and then look > for lower iova pfn's for free iova and as they aren't any, iova alloc > fails though there is 12MB of free iova space. > > To avoid such iova search failures do a retry from the last rb tree node > when iova search fails, this will search the entire tree and get an iova > if its available. > > Signed-off-by: Vijayanand Jitta > --- > drivers/iommu/iova.c | 23 +++++++++++++++++------ > 1 file changed, 17 insertions(+), 6 deletions(-) > > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c > index 49fc01f..4e77116 100644 > --- a/drivers/iommu/iova.c > +++ b/drivers/iommu/iova.c > @@ -184,8 +184,9 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad, > struct rb_node *curr, *prev; > struct iova *curr_iova; > unsigned long flags; > - unsigned long new_pfn; > + unsigned long new_pfn, low_pfn_new; > unsigned long align_mask = ~0UL; > + unsigned long high_pfn = limit_pfn, low_pfn = iovad->start_pfn; > > if (size_aligned) > align_mask <<= fls_long(size - 1); > @@ -198,15 +199,25 @@ static int __alloc_and_insert_iova_range(struct iova_domain *iovad, > > curr = __get_cached_rbnode(iovad, limit_pfn); > curr_iova = rb_entry(curr, struct iova, node); > + low_pfn_new = curr_iova->pfn_hi + 1; Could we call "low_pfn_new" something like "retry_pfn" instead? This code already has unavoidable readability struggles with so many different "pfn"s in play, so having two different meanings of "new" really doesn't help. Other than that, I think this looks OK (IIRC it's basically what I originally suggested), so with the naming tweaked, Reviewed-by: Robin Murphy > + > +retry: > do { > - limit_pfn = min(limit_pfn, curr_iova->pfn_lo); > - new_pfn = (limit_pfn - size) & align_mask; > + high_pfn = min(high_pfn, curr_iova->pfn_lo); > + new_pfn = (high_pfn - size) & align_mask; > prev = curr; > curr = rb_prev(curr); > curr_iova = rb_entry(curr, struct iova, node); > - } while (curr && new_pfn <= curr_iova->pfn_hi); > - > - if (limit_pfn < size || new_pfn < iovad->start_pfn) { > + } while (curr && new_pfn <= curr_iova->pfn_hi && new_pfn >= low_pfn); > + > + if (high_pfn < size || new_pfn < low_pfn) { > + if (low_pfn == iovad->start_pfn && low_pfn_new < limit_pfn) { > + high_pfn = limit_pfn; > + low_pfn = low_pfn_new; > + curr = &iovad->anchor.node; > + curr_iova = rb_entry(curr, struct iova, node); > + goto retry; > + } > iovad->max32_alloc_size = size; > goto iova32_full; > } > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu