Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752784AbdFTXZX (ORCPT ); Tue, 20 Jun 2017 19:25:23 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:52452 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752417AbdFTXZW (ORCPT ); Tue, 20 Jun 2017 19:25:22 -0400 Date: Tue, 20 Jun 2017 16:25:07 -0700 From: Ram Pai To: Anshuman Khandual Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, dave.hansen@intel.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com Subject: Re: [RFC v2 02/12] powerpc: Free up four 64K PTE bits in 64K backed hpte pages. Reply-To: Ram Pai References: <1497671564-20030-1-git-send-email-linuxram@us.ibm.com> <1497671564-20030-3-git-send-email-linuxram@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-12-10) X-TM-AS-GCONF: 00 x-cbid: 17062023-0028-0000-0000-000007DA1478 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007263; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00877652; UDB=6.00437227; IPR=6.00657791; BA=6.00005432; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015904; XFM=3.00000015; UTC=2017-06-20 23:25:18 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17062023-0029-0000-0000-0000364F9BFE Message-Id: <20170620232507.GG17588@ram.oc3035372033.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-06-20_12:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=2 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1706200403 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1080 Lines: 29 On Tue, Jun 20, 2017 at 04:21:45PM +0530, Anshuman Khandual wrote: > On 06/17/2017 09:22 AM, Ram Pai wrote: > > Rearrange 64K PTE bits to free up bits 3, 4, 5 and 6 > > in the 64K backed hpte pages. This along with the earlier > > patch will entirely free up the four bits from 64K PTE. > > > > This patch does the following change to 64K PTE that is > > backed by 64K hpte. > > > > H_PAGE_F_SECOND which occupied bit 4 moves to the second part > > of the pte. > > H_PAGE_F_GIX which occupied bit 5, 6 and 7 also moves to the > > second part of the pte. > > > > since bit 7 is now freed up, we move H_PAGE_BUSY from bit 9 > > to bit 7. Trying to minimize gaps so that contiguous bits > > can be allocated if needed in the future. > > > > The second part of the PTE will hold > > (H_PAGE_F_SECOND|H_PAGE_F_GIX) at bit 60,61,62,63. > > I still dont understand how we freed up the 5th bit which is > used in the 5th patch. Was that bit never used for any thing > on 64K page size (64K and 4K mappings) ? yes. it was not used. So I gladly used it :-) RP