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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 EF337C388F9 for ; Mon, 26 Oct 2020 17:35:51 +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 A004C21D42 for ; Mon, 26 Oct 2020 17:35:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A004C21D42 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 silver.osuosl.org (Postfix) with ESMTP id 580192E132; Mon, 26 Oct 2020 17:35:51 +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 ftYCK6itR56r; Mon, 26 Oct 2020 17:35:49 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by silver.osuosl.org (Postfix) with ESMTP id 5FCEF2E11B; Mon, 26 Oct 2020 17:35:49 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 4BE05C1AD4; Mon, 26 Oct 2020 17:35:49 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 9D8AEC0051 for ; Mon, 26 Oct 2020 17:35:46 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 95DAE2E12A for ; Mon, 26 Oct 2020 17:35:46 +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 mHl2chN69eMt for ; Mon, 26 Oct 2020 17:35:40 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from szxga05-in.huawei.com (szxga05-in.huawei.com [45.249.212.191]) by silver.osuosl.org (Postfix) with ESMTPS id 890E32741E for ; Mon, 26 Oct 2020 17:35:39 +0000 (UTC) Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4CKhnT1v2lzLnDk; Tue, 27 Oct 2020 01:35:41 +0800 (CST) Received: from localhost.localdomain (10.69.192.58) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.487.0; Tue, 27 Oct 2020 01:35:28 +0800 From: John Garry To: , Subject: [PATCH v2 3/4] iommu/iova: Flush CPU rcache for when a depot fills Date: Tue, 27 Oct 2020 01:31:40 +0800 Message-ID: <1603733501-211004-4-git-send-email-john.garry@huawei.com> X-Mailer: git-send-email 2.8.1 In-Reply-To: <1603733501-211004-1-git-send-email-john.garry@huawei.com> References: <1603733501-211004-1-git-send-email-john.garry@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.69.192.58] X-CFilter-Loop: Reflected Cc: linuxarm@huawei.com, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, xiyou.wangcong@gmail.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" Leizhen reported some time ago that IOVA performance may degrade over time [0], but unfortunately his solution to fix this problem was not given attention. To summarize, the issue is that as time goes by, the CPU rcache and depot rcache continue to grow. As such, IOVA RB tree access time also continues to grow. At a certain point, a depot may become full, and also some CPU rcaches may also be full when inserting another IOVA is attempted. For this scenario, currently the "loaded" CPU rcache is freed and a new one is created. This freeing means that many IOVAs in the RB tree need to be freed, which makes IO throughput performance fall off a cliff in some storage scenarios: Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6314MB/0KB/0KB /s] [1616K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [5669MB/0KB/0KB /s] [1451K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6031MB/0KB/0KB /s] [1544K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6673MB/0KB/0KB /s] [1708K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6705MB/0KB/0KB /s] [1717K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6031MB/0KB/0KB /s] [1544K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6761MB/0KB/0KB /s] [1731K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6705MB/0KB/0KB /s] [1717K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6685MB/0KB/0KB /s] [1711K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6178MB/0KB/0KB /s] [1582K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [6731MB/0KB/0KB /s] [1723K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [2387MB/0KB/0KB /s] [611K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [2689MB/0KB/0KB /s] [688K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [2278MB/0KB/0KB /s] [583K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [1288MB/0KB/0KB /s] [330K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [1632MB/0KB/0KB /s] [418K/0/0 iops] Jobs: 12 (f=12): [RRRRRRRRRRRR] [0.0% done] [1765MB/0KB/0KB /s] [452K/0/0 iops] And continue in this fashion, without recovering. Note that in this example it was required to wait 16 hours for this to occur. Also note that IO throughput also becomes gradually becomes more unstable leading up to this point. As a solution to this issue, judge that the IOVA caches have grown too big when cached magazines need to be free, and just flush all the CPUs rcaches instead. The depot rcaches, however, are not flushed, as they can be used to immediately replenish active CPUs. In future, some IOVA compaction could be implemented to solve the instabilty issue, which I figure could be quite complex to implement. [0] https://lore.kernel.org/linux-iommu/20190815121104.29140-3-thunder.leizhen@huawei.com/ Analyzed-by: Zhen Lei Reported-by: Xiang Chen Signed-off-by: John Garry --- drivers/iommu/iova.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index 1f3f0f8b12e0..386005055aca 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -901,7 +901,6 @@ static bool __iova_rcache_insert(struct iova_domain *iovad, struct iova_rcache *rcache, unsigned long iova_pfn) { - struct iova_magazine *mag_to_free = NULL; struct iova_cpu_rcache *cpu_rcache; bool can_insert = false; unsigned long flags; @@ -923,13 +922,12 @@ static bool __iova_rcache_insert(struct iova_domain *iovad, if (cpu_rcache->loaded) rcache->depot[rcache->depot_size++] = cpu_rcache->loaded; - } else { - mag_to_free = cpu_rcache->loaded; + can_insert = true; + cpu_rcache->loaded = new_mag; } spin_unlock(&rcache->lock); - - cpu_rcache->loaded = new_mag; - can_insert = true; + if (!can_insert) + iova_magazine_free(new_mag); } } @@ -938,10 +936,8 @@ static bool __iova_rcache_insert(struct iova_domain *iovad, spin_unlock_irqrestore(&cpu_rcache->lock, flags); - if (mag_to_free) { - iova_magazine_free_pfns(mag_to_free, iovad); - iova_magazine_free(mag_to_free); - } + if (!can_insert) + free_all_cpu_cached_iovas(iovad); return can_insert; } -- 2.26.2 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu