From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758854AbcG1BNt (ORCPT ); Wed, 27 Jul 2016 21:13:49 -0400 Received: from mga09.intel.com ([134.134.136.24]:26382 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751229AbcG1BNj convert rfc822-to-8bit (ORCPT ); Wed, 27 Jul 2016 21:13:39 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,432,1464678000"; d="scan'208";a="1030475582" From: "Li, Liang Z" To: "Hansen, Dave" , "linux-kernel@vger.kernel.org" CC: "virtualization@lists.linux-foundation.org" , "linux-mm@kvack.org" , "virtio-dev@lists.oasis-open.org" , "kvm@vger.kernel.org" , "qemu-devel@nongnu.org" , "dgilbert@redhat.com" , "quintela@redhat.com" , "Michael S. Tsirkin" , Andrew Morton , Vlastimil Babka , Mel Gorman , Paolo Bonzini , "Cornelia Huck" , Amit Shah Subject: RE: [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate process Thread-Topic: [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate process Thread-Index: AQHR56aT5WMR4KLffEuOEzyB2S9p86Ar62GAgAEO6BA= Date: Thu, 28 Jul 2016 01:13:35 +0000 Message-ID: References: <1469582616-5729-1-git-send-email-liang.z.li@intel.com> <1469582616-5729-5-git-send-email-liang.z.li@intel.com> <5798DB49.7030803@intel.com> In-Reply-To: <5798DB49.7030803@intel.com> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiYmExOWNjZWUtYmUzYi00ZjFhLWIxZWMtNjdmNzhkODQ2MTE1IiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX0lDIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE1LjkuNi42IiwiVHJ1c3RlZExhYmVsSGFzaCI6ImJsNmkzUlNjbndDanN5Q2dmN0RQSXpvcGJBSUtCVldlUVdkYlZ6TnpUQnc9In0= x-ctpclassification: CTP_IC x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Subject: Re: [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate > process > > On 07/26/2016 06:23 PM, Liang Li wrote: > > + vb->pfn_limit = VIRTIO_BALLOON_PFNS_LIMIT; > > + vb->pfn_limit = min(vb->pfn_limit, get_max_pfn()); > > + vb->bmap_len = ALIGN(vb->pfn_limit, BITS_PER_LONG) / > > + BITS_PER_BYTE + 2 * sizeof(unsigned long); > > + hdr_len = sizeof(struct balloon_bmap_hdr); > > + vb->bmap_hdr = kzalloc(hdr_len + vb->bmap_len, GFP_KERNEL); > > This ends up doing a 1MB kmalloc() right? That seems a _bit_ big. How big > was the pfn buffer before? Yes, it is if the max pfn is more than 32GB. The size of the pfn buffer use before is 256*4 = 1024 Bytes, it's too small, and it's the main reason for bad performance. Use the max 1MB kmalloc is a balance between performance and flexibility, a large page bitmap covers the range of all the memory is no good for a system with huge amount of memory. If the bitmap is too small, it means we have to traverse a long list for many times, and it's bad for performance. Thanks! Liang