From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-1.mimecast.com ([207.211.31.81]:46059 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727205AbgBDNjC (ORCPT ); Tue, 4 Feb 2020 08:39:02 -0500 Subject: Re: [PATCH v6 10/10] mm/memory_hotplug: Cleanup __remove_pages() References: <20191006085646.5768-1-david@redhat.com> <20191006085646.5768-11-david@redhat.com> <20200204094652.GE6494@linux> <5d698f94-af18-0714-bc97-14b6c520572c@redhat.com> <20200204131353.GJ22482@gate.crashing.org> From: David Hildenbrand Message-ID: <0e2f700c-b01b-8c16-99c2-2648967fc203@redhat.com> Date: Tue, 4 Feb 2020 14:38:51 +0100 MIME-Version: 1.0 In-Reply-To: <20200204131353.GJ22482@gate.crashing.org> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Sender: linux-s390-owner@vger.kernel.org List-ID: To: Segher Boessenkool Cc: Oscar Salvador , linux-s390@vger.kernel.org, Michal Hocko , linux-ia64@vger.kernel.org, Pavel Tatashin , linux-sh@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Wei Yang , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Dan Williams , linux-arm-kernel@lists.infradead.org On 04.02.20 14:13, Segher Boessenkool wrote: > On Tue, Feb 04, 2020 at 01:41:06PM +0100, David Hildenbrand wrote: >> On 04.02.20 10:46, Oscar Salvador wrote: >>> I have to confess that it took me while to wrap around my head >>> with the new min() change, but looks ok: >> >> It's a pattern commonly used in compilers and emulators to calculate t= he >> number of bytes to the next block/alignment. (we're missing a macro >> (like we have ALIGN_UP/IS_ALIGNED) for that - but it's hard to come up >> with a good name (e.g., SIZE_TO_NEXT_ALIGN) . >=20 > You can just write the easy to understand >=20 > ... ALIGN_UP(x) - x ... you mean ALIGN_UP(x, PAGES_PER_SECTION) - x but ... >=20 > which is better *without* having a separate name. Does that not > generate good machine code for you? 1. There is no ALIGN_UP. "SECTION_ALIGN_UP(x) - x" would be possible 2. It would be wrong if x is already aligned. e.g., let's use 4096 for simplicity as we all know that value by heart (for both x and the block size). a) -(4096 | -4096) -> 4096 b) #define ALIGN_UP(x, a) ((x + a - 1) & -(a)) ALIGN_UP(4096, 4096) - 4096 -> 0 Not as easy as it seems ... --=20 Thanks, David / dhildenb