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a=rsa-sha256; c=relaxed/relaxed; d=pankajraghav.com; s=MBO0001; t=1717842181; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=CN42FyvMLfGhJvGBn6PDLQsQ9W8XHB0kTB0fHm6THX4=; b=URCHGk+Q/pp8GE03XIx3TgAxSXlyfltHrc7ciz8ok/N9IWHKZLo0jcuNLFJvMBZea/mOYj qTfORTIpOljo+10Nogd6KizUXFUfk0gz1tblu/FuEXezTBb/yvSv0DJ2sEGnEfD7DUGkFe 3Wdm8FjCTUys9nwkX8Ww6JIxzOdvFN4wDiGkzwpSX7w/3O5wOdlHOsqiRKOYMtwXkLbdCa VSTxIlmqKSjtVSe14q1oLJo8nDEiemQDhrYWMMZfu5N6Ug2GSA/zEU7nvs5DVQoHfWbvbL 3agMAx0T5waM5bF3iVr40vm02yirSz6xVimYGq7aTRQkT+vyp4Xn6Kzu8aKr5w== Date: Sat, 8 Jun 2024 10:22:57 +0000 From: "Pankaj Raghav (Samsung)" To: Andrew Morton Cc: Shuah Khan , linux-mm@kvack.org, gost.dev@samsung.com, David Hildenbrand , willy@infradead.org, mcgrof@kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Zi Yan , Pankaj Raghav Subject: Re: [PATCH v3] selftests/mm: use asm volatile to not optimize mmap read variable Message-ID: <20240608102257.edfsoqn7dt4s47p3@quentin> References: <20240606203619.677276-1-kernel@pankajraghav.com> <20240607213936.a58028617aacdbf6913d3735@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240607213936.a58028617aacdbf6913d3735@linux-foundation.org> X-Rspamd-Queue-Id: F4209160005 X-Rspam-User: X-Rspamd-Server: rspam12 X-Stat-Signature: k9bphnb7gukuu74tt5wgpwjo4f5uzwsf X-HE-Tag: 1717842186-627216 X-HE-Meta: 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 b5SbCpGY lxdXHqK5evgl+rV4sOk2WXUk/V+fpzYEQ0C12ZJ4acZq+xl4uxR6JbTEFqEcPWOQMPF+QNbUT8ocXhNQjrbSsIwozvH0SwEh18+qoqttOwC96GGw3b1F332RSkMXoJHevi+x2Wj36ay2dIsrAjpXHjseQfWmXFZ4WOUm+qnSoMI7GRQl8MbVwxtVfn62Z6WxRJXStJ0Ap0/pEbozNq9lqjLEnpsmOpuqNxCBO7IJmoLMqE5jr6fpy29dBG0XnGwk+YIms007xflHm/kGdQa4K05EbY+6QCfnsBxwLbP1hE/G4t8A= 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: On Fri, Jun 07, 2024 at 09:39:36PM -0700, Andrew Morton wrote: > On Thu, 6 Jun 2024 20:36:19 +0000 "Pankaj Raghav (Samsung)" wrote: > > > From: Pankaj Raghav > > > > create_pagecache_thp_and_fd() in split_huge_page_test.c used the > > variable dummy to perform mmap read. > > > > However, this test was skipped even on XFS which has large folio > > support. The issue was compiler (gcc 13.2.0) was optimizing out the > > dummy variable, therefore, not creating huge page in the page cache. > > > > Use asm volatile() trick to force the compiler not to optimize out > > the loop where we read from the mmaped addr. This is similar to what is > > being done in other tests (cow.c, etc) > > > > As the variable is now used in the asm statement, remove the unused > > attribute. > > > > What are the runtime effects of this change? An inappropriate test > failure? If so, shouldn't we fix 6.9.x kernels also? And is > fc4d182316bd ("mm: huge_memory: enable debugfs to split huge pages to > any order") an appropriate Fixes: target? I mentioned it here in the commit message: However, this test was skipped even on XFS which has large folio support. So the test just skip these cases and does not fail. That is why I didn't use the Fixes tag. Let me know if it needs one. -- Pankaj