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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id c204sm1700580qkb.90.2019.10.09.13.56.28 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Oct 2019 13:56:28 -0700 (PDT) Message-ID: <1570654587.5937.18.camel@lca.pw> Subject: Re: [PATCH] shmem: make shmem default size a define value From: Qian Cai To: -Gary- Cc: Vlastimil Babka , Hugh Dickins , linux-mm@kvack.org Date: Wed, 09 Oct 2019 16:56:27 -0400 In-Reply-To: <20191009201745.GF22291@spider> References: <20191009184604.GA5162@spider> <1570647695.5937.16.camel@lca.pw> <20191009201745.GF22291@spider> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 2019-10-09 at 13:17 -0700, -Gary- wrote: > > > @@ -125,14 +128,14 @@ struct shmem_options { > > > #ifdef CONFIG_TMPFS > > > static unsigned long shmem_default_max_blocks(void) > > > { > > > - return totalram_pages() / 2; > > > + return SHMEM_SIZE_DEFAULT; > > > } > > > > > > static unsigned long shmem_default_max_inodes(void) > > > { > > > unsigned long nr_pages = totalram_pages(); > > > > This is now unused. > > Mind telling me what I missed, Qian? > > I pulled from: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > > Latest commit is: > 2019-10-08 15:36:04 -0700 e3280b54afed870d531571212f1fc375df39b7d2 Merge tag 'led-fixes-for-5.4-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds > > My patch is based on that, where the above code still exists, and nr_pages is still referenced below. Apparently, it is making totalram_pages atomic, according to the commit that changed it: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/diff/mm/shmem.c?id=ca79b0c211af63fa3276f0e3fd7dd9ada2439839 > > Should I be pulling from somewhere else, or also re-hacking nr_pages somehow? Ah, you are right that nr_pages is still referenced, but then there could a potentially out of sync? Would that be a problem? Is the compiler just smart enough to call totalram_pages() only once? CPU0: CPU1: unsigned long nr_pages = totalram_pages(); totalram_pages_inc() min(nr_pages - totalhigh_pages(), SHMEM_SIZE_DEFAULT); > > -- Gary > > > > - return min(nr_pages - totalhigh_pages(), nr_pages / 2); > > > + return min(nr_pages - totalhigh_pages(), SHMEM_SIZE_DEFAULT); > > > } > > > #endif