From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3zrmfC3z7HzF1GN for ; Wed, 28 Feb 2018 18:00:03 +1100 (AEDT) Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w1S6xQ1N142158 for ; Wed, 28 Feb 2018 02:00:00 -0500 Received: from e18.ny.us.ibm.com (e18.ny.us.ibm.com [129.33.205.208]) by mx0a-001b2d01.pphosted.com with ESMTP id 2gdm16xp3n-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 28 Feb 2018 01:59:59 -0500 Received: from localhost by e18.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 28 Feb 2018 01:59:58 -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 MIME-Version: 1.0 In-Reply-To: <20180228165331.6e09959d@roar.ozlabs.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Message-Id: <1f14fec4-a2b9-30c8-4c73-ecf00dbba0d7@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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