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Tue, 20 Oct 2020 09:17:31 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 0F1C9C43387; Tue, 20 Oct 2020 09:17:30 +0000 (UTC) Received: from [192.168.0.103] (unknown [106.0.37.58]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: vjitta) by smtp.codeaurora.org (Postfix) with ESMTPSA id 24665C433CB; Tue, 20 Oct 2020 09:17:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 24665C433CB Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=vjitta@codeaurora.org Subject: Re: [PATCH v5 1/2] iommu/iova: Retry from last rb tree node if iova search fails To: joro@8bytes.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <1601451864-5956-1-git-send-email-vjitta@codeaurora.org> From: Vijayanand Jitta Message-ID: <7705f57b-54d1-9c0a-2d41-c1309b0e7168@codeaurora.org> Date: Tue, 20 Oct 2020 14:47:06 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <1601451864-5956-1-git-send-email-vjitta@codeaurora.org> Content-Language: en-GB Cc: robin.murphy@arm.com, 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 9/30/2020 1:14 PM, 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 > Reviewed-by: Robin Murphy > --- > 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 30d969a..c3a1a8e 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, retry_pfn; > 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); > + retry_pfn = curr_iova->pfn_hi + 1; > + > +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 && retry_pfn < limit_pfn) { > + high_pfn = limit_pfn; > + low_pfn = retry_pfn; > + curr = &iovad->anchor.node; > + curr_iova = rb_entry(curr, struct iova, node); > + goto retry; > + } > iovad->max32_alloc_size = size; > goto iova32_full; > } > Gentle ping. Thanks, Vijay -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu