From nobody Tue Dec 16 09:00:22 2025 Delivered-To: importer@patchew.org Received-SPF: temperror (zoho.com: Error in retrieving data from DNS) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=temperror (zoho.com: Error in retrieving data from DNS) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (208.118.235.17 [208.118.235.17]) by mx.zohomail.com with SMTPS id 1512589311540490.06679064350465; Wed, 6 Dec 2017 11:41:51 -0800 (PST) Received: from localhost ([::1]:57307 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eMfZX-0007hc-Iy for importer@patchew.org; Wed, 06 Dec 2017 14:41:35 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49094) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eMfCG-0000VJ-KZ for qemu-devel@nongnu.org; Wed, 06 Dec 2017 14:17:35 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eMfCD-0000Pm-Gm for qemu-devel@nongnu.org; Wed, 06 Dec 2017 14:17:32 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:47330 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eMfCD-0000Oy-BC for qemu-devel@nongnu.org; Wed, 06 Dec 2017 14:17:29 -0500 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id vB6JE3jg015520 for ; Wed, 6 Dec 2017 14:17:28 -0500 Received: from e17.ny.us.ibm.com (e17.ny.us.ibm.com [129.33.205.207]) by mx0b-001b2d01.pphosted.com with ESMTP id 2epn0ac18d-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 06 Dec 2017 14:17:28 -0500 Received: from localhost by e17.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Wed, 6 Dec 2017 14:17:24 -0500 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id vB6JHOqV34471988; Wed, 6 Dec 2017 19:17:24 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 52329B204E; Wed, 6 Dec 2017 14:14:31 -0500 (EST) Received: from localhost (unknown [9.80.93.86]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP id 059E9B204D; Wed, 6 Dec 2017 14:14:30 -0500 (EST) From: Michael Roth To: qemu-devel@nongnu.org Date: Wed, 6 Dec 2017 13:16:17 -0600 X-Mailer: git-send-email 2.11.0 In-Reply-To: <20171206191648.18208-1-mdroth@linux.vnet.ibm.com> References: <20171206191648.18208-1-mdroth@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17120619-0040-0000-0000-000003CDAF48 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008161; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000244; SDB=6.00956379; UDB=6.00483442; IPR=6.00736416; BA=6.00005729; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00018387; XFM=3.00000015; UTC=2017-12-06 19:17:26 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17120619-0041-0000-0000-000007C2E7D9 Message-Id: <20171206191648.18208-25-mdroth@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-12-06_07:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=29 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1712060273 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.158.5 Subject: [Qemu-devel] [PATCH 24/55] memory: Share special empty FlatView X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , Paolo Bonzini , qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_6 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Alexey Kardashevskiy This shares an cached empty FlatView among address spaces. The empty FV is used every time when a root MR renders into a FV without memory sections which happens when MR or its children are not enabled or zero-sized. The empty_view is not NULL to keep the rest of memory API intact; it also has a dispatch tree for the same reason. On POWER8 with 255 CPUs, 255 virtio-net, 40 PCI bridges guest this halves the amount of FlatView's in use (557 -> 260) and dispatch tables (~800000 -> ~370000). In an unrelated experiment with 112 non-virtio devices on x86 ("-M pc"), only 4 FlatViews are alive, and about ~2000 are created at startup. Signed-off-by: Alexey Kardashevskiy Message-Id: <20170921085110.25598-16-aik@ozlabs.ru> Signed-off-by: Paolo Bonzini (cherry picked from commit 092aa2fc65b7a35121616aad8f39d47b8f921618) Signed-off-by: Michael Roth --- memory.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/memory.c b/memory.c index 231bb78fa7..d90853855b 100644 --- a/memory.c +++ b/memory.c @@ -317,6 +317,7 @@ static void flatview_unref(FlatView *view) { if (atomic_fetch_dec(&view->ref) =3D=3D 1) { trace_flatview_destroy_rcu(view, view->root); + assert(view->root); call_rcu(view, flatview_destroy, rcu); } } @@ -760,16 +761,19 @@ static MemoryRegion *memory_region_get_flatview_root(= MemoryRegion *mr) } } } + if (found =3D=3D 0) { + return NULL; + } if (next) { mr =3D next; continue; } } =20 - break; + return mr; } =20 - return mr; + return NULL; } =20 /* Render a memory topology into a list of disjoint absolute ranges. */ @@ -965,12 +969,22 @@ static void address_space_update_topology_pass(Addres= sSpace *as, =20 static void flatviews_init(void) { + static FlatView *empty_view; + if (flat_views) { return; } =20 flat_views =3D g_hash_table_new_full(g_direct_hash, g_direct_equal, NU= LL, (GDestroyNotify) flatview_unref); + if (!empty_view) { + empty_view =3D generate_memory_topology(NULL); + /* We keep it alive forever in the global variable. */ + flatview_ref(empty_view); + } else { + g_hash_table_replace(flat_views, NULL, empty_view); + flatview_ref(empty_view); + } } =20 static void flatviews_reset(void) --=20 2.11.0