From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-x235.google.com (mail-pl0-x235.google.com [IPv6:2607:f8b0:400e:c01::235]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3zsRm70sTBzF1hN for ; Thu, 1 Mar 2018 20:22:30 +1100 (AEDT) Received: by mail-pl0-x235.google.com with SMTP id d4-v6so3313037pll.5 for ; Thu, 01 Mar 2018 01:22:30 -0800 (PST) Date: Thu, 1 Mar 2018 19:22:15 +1000 From: Nicholas Piggin To: Christophe LEROY Cc: "Aneesh Kumar K.V" , Michael Ellerman , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [RFC REBASED 5/5] powerpc/mm/slice: use the dynamic high slice size to limit bitmap operations Message-ID: <20180301192215.0872484d@roar.ozlabs.ibm.com> In-Reply-To: <4e3c5281-427b-abe8-9c80-f2c1a0247e28@c-s.fr> 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> <4e3c5281-427b-abe8-9c80-f2c1a0247e28@c-s.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 1 Mar 2018 08:09:55 +0100 Christophe LEROY wrote: > Le 28/02/2018 à 07:53, Nicholas Piggin a écrit : > > 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. > > > > I'm not really taking care of your serie, just took it once to see how > it fits on the 8xx. > I prefer if you can handle them. If you need my help for any test on > PPC32 don't hesitate to ask. No problem I can do that. Thanks for rebasing them. Thanks, Nick