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[35.238.199.243]) by smtp.gmail.com with ESMTPSA id l11sm15495000ios.8.2021.07.21.14.07.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Jul 2021 14:07:59 -0700 (PDT) Date: Wed, 21 Jul 2021 21:07:08 +0000 From: Dennis Zhou To: Yury Norov Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-mmc@vger.kernel.org, Andy Shevchenko , Rasmus Villemoes , Petr Mladek , Sergey Senozhatsky , Tejun Heo , Steven Rostedt , Wolfram Sang , Ulf Hansson , Christoph Lameter , Andrew Morton Subject: Re: [PATCH 1/4] mm/percpu: micro-optimize pcpu_is_populated() Message-ID: References: <20210719021755.883182-1-yury.norov@gmail.com> <20210719021755.883182-2-yury.norov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210719021755.883182-2-yury.norov@gmail.com> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 7A199D00E8B7 X-Stat-Signature: hebo6dpmtx1phmeypgyzgwjtfei65hrc Authentication-Results: imf21.hostedemail.com; dkim=none; spf=pass (imf21.hostedemail.com: domain of dennisszhou@gmail.com designates 209.85.166.53 as permitted sender) smtp.mailfrom=dennisszhou@gmail.com; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=kernel.org (policy=none) X-HE-Tag: 1626901702-539280 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: Hello, On Sun, Jul 18, 2021 at 07:17:52PM -0700, Yury Norov wrote: > bitmap_next_clear_region() calls find_next_zero_bit() and find_next_bit() > sequentially to find a range of clear bits. In case of pcpu_is_populated() > there's a chance to return earlier if bitmap has all bits set. > > Signed-off-by: Yury Norov > --- > mm/percpu.c | 15 ++++++++------- > 1 file changed, 8 insertions(+), 7 deletions(-) > > diff --git a/mm/percpu.c b/mm/percpu.c > index 7f2e0151c4e2..25461571dcc5 100644 > --- a/mm/percpu.c > +++ b/mm/percpu.c > @@ -1071,17 +1071,18 @@ static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off, > static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits, > int *next_off) > { > - unsigned int page_start, page_end, rs, re; > + unsigned int start, end; > > - page_start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE); > - page_end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE); > + start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE); > + end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE); > > - rs = page_start; > - bitmap_next_clear_region(chunk->populated, &rs, &re, page_end); > - if (rs >= page_end) > + start = find_next_zero_bit(chunk->populated, end, start); > + if (start >= end) > return true; > > - *next_off = re * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE; > + end = find_next_bit(chunk->populated, end, start + 1); > + > + *next_off = end * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE; > return false; > } > > -- > 2.30.2 > Sorry for the delay. Acked-by: Dennis Zhou Thanks, Dennis