From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752002AbeB1HAB (ORCPT ); Wed, 28 Feb 2018 02:00:01 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:55604 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751717AbeB1HAA (ORCPT ); Wed, 28 Feb 2018 02:00:00 -0500 Subject: Re: [RFC REBASED 5/5] powerpc/mm/slice: use the dynamic high slice size to limit bitmap operations To: Nicholas Piggin Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <02a62db83282b5ef3e0e8281fdc46fa91beffc86.1518382747.git.christophe.leroy@c-s.fr> <5badd882663833576c10b8aafe235fe1e443f119.1518382747.git.christophe.leroy@c-s.fr> <87bmga7qng.fsf@linux.vnet.ibm.com> <20180227191125.659d5cbe@roar.ozlabs.ibm.com> <878tbe7ggs.fsf@linux.vnet.ibm.com> <20180228165331.6e09959d@roar.ozlabs.ibm.com> From: "Aneesh Kumar K.V" Date: Wed, 28 Feb 2018 12:29:52 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180228165331.6e09959d@roar.ozlabs.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18022806-0044-0000-0000-000003EB2F21 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008601; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000254; SDB=6.00996192; UDB=6.00506426; IPR=6.00775515; MB=3.00019772; MTD=3.00000008; XFM=3.00000015; UTC=2018-02-28 06:59:57 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18022806-0045-0000-0000-0000081B3ACE Message-Id: <1f14fec4-a2b9-30c8-4c73-ecf00dbba0d7@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-02-28_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 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-1802280083 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/28/2018 12:23 PM, Nicholas Piggin wrote: > On Tue, 27 Feb 2018 18:11:07 +0530 > "Aneesh Kumar K.V" wrote: > >> Nicholas Piggin writes: >> >>> On Tue, 27 Feb 2018 14:31:07 +0530 >>> "Aneesh Kumar K.V" wrote: >>> >>>> Christophe Leroy writes: >>>> >>>>> The number of high slices a process might use now depends on its >>>>> address space size, and what allocation address it has requested. >>>>> >>>>> This patch uses that limit throughout call chains where possible, >>>>> rather than use the fixed SLICE_NUM_HIGH for bitmap operations. >>>>> This saves some cost for processes that don't use very large address >>>>> spaces. >>>> >>>> I haven't really looked at the final code. One of the issue we had was >>>> with the below scenario. >>>> >>>> mmap(addr, len) where addr < 128TB and addr+len > 128TB We want to make >>>> sure we build the mask such that we don't find the addr available. >>> >>> We should run it through the mmap regression tests. I *think* we moved >>> all of that logic from the slice code to get_ummapped_area before going >>> in to slices. I may have missed something though, it would be good to >>> have more eyes on it. >>> >> >> mmap(-1,...) failed with the test. Something like below fix it >> >> @@ -756,7 +770,7 @@ void slice_set_user_psize(struct mm_struct *mm, unsigned int psize) >> mm->context.low_slices_psize = lpsizes; >> >> hpsizes = mm->context.high_slices_psize; >> - high_slices = GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit); >> + high_slices = SLICE_NUM_HIGH; >> for (i = 0; i < high_slices; i++) { >> mask_index = i & 0x1; >> index = i >> 1; >> >> I guess for everything in the mm_context_t, we should compute it till >> SLICE_NUM_HIGH. The reason for failure was, even though we recompute the >> slice mask cached in mm_context on slb_addr_limit, it was still derived >> from the high_slices_psizes which was computed with lower value. > > Okay thanks for catching that Aneesh. I guess that's a slow path so it > should be okay. Christophe if you're taking care of the series can you > fold it in? Otherwise I'll do that after yours gets merged. > should we also compute the mm_context_t.slice_mask using SLICE_NUM_HIGH and skip the recalc_slice_mask_cache when we change the addr limit? -aneesh