From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-x22f.google.com (mail-pg0-x22f.google.com [IPv6:2607:f8b0:400e:c05::22f]) (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 3zrCcV0ng4zF1X0 for ; Tue, 27 Feb 2018 20:11:37 +1100 (AEDT) Received: by mail-pg0-x22f.google.com with SMTP id g12so7293284pgs.0 for ; Tue, 27 Feb 2018 01:11:37 -0800 (PST) Date: Tue, 27 Feb 2018 19:11:25 +1000 From: Nicholas Piggin To: "Aneesh Kumar K.V" Cc: Christophe Leroy , 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: <20180227191125.659d5cbe@roar.ozlabs.ibm.com> In-Reply-To: <87bmga7qng.fsf@linux.vnet.ibm.com> References: <02a62db83282b5ef3e0e8281fdc46fa91beffc86.1518382747.git.christophe.leroy@c-s.fr> <5badd882663833576c10b8aafe235fe1e443f119.1518382747.git.christophe.leroy@c-s.fr> <87bmga7qng.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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. Thanks, Nick