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Tue, 23 Apr 2024 22:12:03 -0700 (PDT) Date: Tue, 23 Apr 2024 22:12:00 -0700 From: Dennis Zhou To: Yuntao Wang Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dennis Zhou , Tejun Heo , Christoph Lameter , Andrew Morton Subject: Re: [PATCH] percpu: simplify the logic of pcpu_alloc_first_chunk() Message-ID: References: <20240423135525.36872-1-ytcoode@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240423135525.36872-1-ytcoode@gmail.com> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: B924F160011 X-Stat-Signature: s3i54e8mwqtmktuacexetkwqjf8aoz6c X-HE-Tag: 1713935524-766070 X-HE-Meta: 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 eFWIYJxv 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Yuntao, On Tue, Apr 23, 2024 at 09:55:25PM +0800, Yuntao Wang wrote: > In the logic for hiding the end of the bitmap, there are several places > where the same value 'region_bits - offset_bits' is calculated over and > over again using different methods. Eliminate these redundant calculations > to improve code readability. > > Signed-off-by: Yuntao Wang > --- > mm/percpu.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/mm/percpu.c b/mm/percpu.c > index 4e11fc1e6def..2a051f00f68d 100644 > --- a/mm/percpu.c > +++ b/mm/percpu.c > @@ -1421,15 +1421,13 @@ static struct pcpu_chunk * __init pcpu_alloc_first_chunk(unsigned long tmp_addr, > if (chunk->end_offset) { > /* hide the end of the bitmap */ > offset_bits = chunk->end_offset / PCPU_MIN_ALLOC_SIZE; > - bitmap_set(chunk->alloc_map, > - pcpu_chunk_map_bits(chunk) - offset_bits, > - offset_bits); > - set_bit((start_offset + map_size) / PCPU_MIN_ALLOC_SIZE, > - chunk->bound_map); > + start_offset = region_bits - offset_bits; Generally I think this makes sense, but I'm less inclined to mix the start_offset variable name in here. A helper function might make this cleaner, consolidating the start_offset and end_offset logic. static void pcpu_chunk_hide_region(chunk, bit_off, bits); Thanks, Dennis > + > + bitmap_set(chunk->alloc_map, start_offset, offset_bits); > + set_bit(start_offset, chunk->bound_map); > set_bit(region_bits, chunk->bound_map); > > - pcpu_block_update_hint_alloc(chunk, pcpu_chunk_map_bits(chunk) > - - offset_bits, offset_bits); > + pcpu_block_update_hint_alloc(chunk, start_offset, offset_bits); > } > > return chunk; > -- > 2.44.0 >