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d=linuxfoundation.org; s=korg; t=1681649403; bh=PwY8QWEnWV0M5kBQ/d61GJUA7etUYjtwdP2PeGi83jg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WVwshLYWCaDWOj6I/QRtAs/yHt1ux/16OP37Q3wiITFXaf7+bxrYH3clC8fGicqQr HaIExs38ECYGHaOFFGiq/E0UMNEGl30mUc1+Y/qm7LVe1V8YRt4j+QAqyHrzS1B2jV sspAKw1EkdCgNXBZXsE0iip8qskxYPygTi/2b4Wc= Date: Sun, 16 Apr 2023 14:50:01 +0200 From: Greg KH To: Luis Chamberlain Cc: Christoph Hellwig , Kees Cook , david@redhat.com, patches@lists.linux.dev, linux-modules@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, pmladek@suse.com, petr.pavlu@suse.com, prarit@redhat.com, torvalds@linux-foundation.org, rafael@kernel.org, christophe.leroy@csgroup.eu, tglx@linutronix.de, peterz@infradead.org, song@kernel.org, rppt@kernel.org, dave@stgolabs.net, willy@infradead.org, vbabka@suse.cz, mhocko@suse.com, dave.hansen@linux.intel.com, colin.i.king@gmail.com, jim.cromie@gmail.com, catalin.marinas@arm.com, jbaron@akamai.com, rick.p.edgecombe@intel.com Subject: Re: [RFC 2/2] kread: avoid duplicates Message-ID: <2023041637-glamorous-appetite-dc12@gregkh> References: <20230414052840.1994456-1-mcgrof@kernel.org> <20230414052840.1994456-3-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 6D8DD18000B X-Stat-Signature: yzsom7niypi6no3fn4unrf15133e67dn X-HE-Tag: 1681649405-42879 X-HE-Meta: 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 KuBMDDSj 2GnFkWqYRbL3IujHG+ovJhIO3WKB5tsMs5H4riwFXZw0lVe0GvV4yUm6ky1t8XOUbHGp2atbSLlDzzL1Y+CYLSxOXWEm3o0Feeb/7iVOWRVB7nTU3d9A1n0ed+7xuR9jgeErNSJuRTmquoK48xqg4WCtnylV59VVJNwcQguTD2trubKJwqEN5ax5C/wMxQGzyxr7cnNNnZ5gC8jnEhT5FqQGnZl2/1UPmgIfc86PYsTFxz69U2bVA5s/l02aqKi+7HjiWCnrgE5sEIoFaXbLQ6eajxYQkER6yIEVDRyytorx/89NpwP9H4FKRyQmCvEAvZcx5l8xecC/43ycJ58IzolnfQhlvEoKqhdjPxECaq/KoFJmZuORTwaTAf0mvwNLMvPMIsuS/2H7VFa7sRhPBazgP3A== 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: On Sat, Apr 15, 2023 at 11:41:28PM -0700, Luis Chamberlain wrote: > On Sat, Apr 15, 2023 at 11:04:12PM -0700, Christoph Hellwig wrote: > > On Thu, Apr 13, 2023 at 10:28:40PM -0700, Luis Chamberlain wrote: > > > With this we run into 0 wasted virtual memory bytes. > > > > Avoid what duplicates? > > David Hildenbrand had reported that with over 400 CPUs vmap space > runs out and it seems it was related to module loading. I took a > look and confirmed it. Module loading ends up requiring in the > worst case 3 vmalloc allocations, so typically at least twice > the size of the module size and in the worst case just add > the decompressed module size: > > a) initial kernel_read*() call > b) optional module decompression > c) the actual module data copy we will keep > > Duplicate module requests that come from userspace end up being thrown > in the trash bin, as only one module will be allocated. Although there > are checks for a module prior to requesting a module udev still doesn't > do the best of a job to avoid that and so we end up with tons of > duplicate module requests. We're talking about gigabytes of vmalloc > bytes just lost because of this for large systems and megabytes for > average systems. So for example with just 255 CPUs we can loose about > 13.58 GiB, and for 8 CPUs about 226.53 MiB. How does the memory get "lost"? Shouldn't it be properly freed when the duplicate module load fails? thanks, greg k-h