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Mon, 26 Sep 2022 13:17:54 -0700 (PDT) Date: Mon, 26 Sep 2022 13:17:53 -0700 From: Yury Norov To: "Aneesh Kumar K.V" Cc: linux-mm@kvack.org, akpm@linux-foundation.org, Wei Xu , Huang Ying , Yang Shi , Davidlohr Bueso , Tim C Chen , Michal Hocko , Linux Kernel Mailing List , Hesham Almatary , Dave Hansen , Jonathan Cameron , Alistair Popple , Dan Williams , Johannes Weiner , jvgediya.oss@gmail.com, Bharata B Rao Subject: Re: [PATCH v15 10/10] lib/nodemask: Optimize node_random for nodemask with single NUMA node Message-ID: References: <20220818131042.113280-1-aneesh.kumar@linux.ibm.com> <20220818131042.113280-11-aneesh.kumar@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220818131042.113280-11-aneesh.kumar@linux.ibm.com> ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=BfqAKVMY; spf=pass (imf29.hostedemail.com: domain of yury.norov@gmail.com designates 209.85.160.170 as permitted sender) smtp.mailfrom=yury.norov@gmail.com; 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spf=pass (imf29.hostedemail.com: domain of yury.norov@gmail.com designates 209.85.160.170 as permitted sender) smtp.mailfrom=yury.norov@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: sd9rqs8mk4zfurfy8qirj51wirzrax1k X-HE-Tag: 1664223475-715636 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: Hi Aneesh, Please CC maintainers in your recipient list. On Thu, Aug 18, 2022 at 06:40:42PM +0530, Aneesh Kumar K.V wrote: > The most common case for certain node_random usage (demotion nodemask) is with > nodemask weight 1. We can avoid calling get_random_init() in that case and > always return the only node set in the nodemask. Can you move the comment about get_random_int() to the code?. > A simple test as below > before = rdtsc_ordered(); > for (i= 0; i < 100; i++) { > rand = node_random(&nmask); > } > after = rdtsc_ordered(); > > Without fix after - before : 16438 > With fix after - before : 816 > > Reviewed-by: "Huang, Ying" > Signed-off-by: Aneesh Kumar K.V > --- > include/linux/nodemask.h | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) > > diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h > index 4b71a96190a8..ac5b6a371be5 100644 > --- a/include/linux/nodemask.h > +++ b/include/linux/nodemask.h > @@ -504,12 +504,21 @@ static inline int num_node_state(enum node_states state) > static inline int node_random(const nodemask_t *maskp) > { > #if defined(CONFIG_NUMA) && (MAX_NUMNODES > 1) > - int w, bit = NUMA_NO_NODE; > + int w, bit; > > w = nodes_weight(*maskp); > - if (w) > + switch (w) { > + case 0: > + bit = NUMA_NO_NODE; > + break; Why not 'return NUMA_NO_NODE' instead of break thing? > + case 1: > + bit = first_node(*maskp); > + break; > + default: > bit = bitmap_ord_to_pos(maskp->bits, > - get_random_int() % w, MAX_NUMNODES); > + get_random_int() % w, MAX_NUMNODES); Don't fix tabs - it trashes the history. > + break; > + } > return bit; > #else > return 0; > -- > 2.37.2 > >