From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Date: Tue, 04 Feb 2020 13:38:51 +0000 Subject: Re: [PATCH v6 10/10] mm/memory_hotplug: Cleanup __remove_pages() Message-Id: <0e2f700c-b01b-8c16-99c2-2648967fc203@redhat.com> List-Id: 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> In-Reply-To: <20200204131353.GJ22482@gate.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Segher Boessenkool Cc: 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, Oscar Salvador 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 the >> 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) . > > You can just write the easy to understand > > ... ALIGN_UP(x) - x ... you mean ALIGN_UP(x, PAGES_PER_SECTION) - x but ... > > 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 ... -- Thanks, David / dhildenb