From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 230FD4EBAD4; Tue, 29 Sep 2026 09:05:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790672732; cv=none; b=met4QskA0Eoxv6PsKz7pMiS3pAT1/MyRqPH0x5ziFEGs13N9cLTs4Wu5P18MuR0pZiwi/VZBb0BZjwouhGL+d9uw0J7JjAMSNAtMllVTT2B+TBZppsWcw28cUgn6b1/ZDsKMhVZSGLCwg575u0v/Z6fNzGEUyMs5FgFuyzJE8mc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790672732; c=relaxed/simple; bh=wxmwOLxAhQpBe7UtMnjFcrSEnz/kEIYY9IPLyMGptV4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rKlx3YNMP/Hk2AjsMxFFLAdDVaMvkYNizNkrsnOdpQjsUHyDEE9wD1VFwIXoPi1OST3xlh40Eurne8LVoNz9LyMnCZJyPyky/XYMPuDC/reiIx5WG0CHdd95Uou2c7lJ7j2a0oWSGSh0Bs0YlTbBqFEuYixb9s7xBx7D++Mw4dE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=AEVzYGRL; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="AEVzYGRL" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ED58A1516; Tue, 29 Sep 2026 02:05:10 -0700 (PDT) Received: from [10.164.19.84] (a081061.arm.com [10.164.19.84]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2D9993F85F; Tue, 29 Sep 2026 02:05:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790672714; bh=wxmwOLxAhQpBe7UtMnjFcrSEnz/kEIYY9IPLyMGptV4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=AEVzYGRLbEG6f0HWOgDUWAZxT88uI/fydL6u0G2bJG0cxIal7ePkx+TDFllEwLf/Y TaT96+nTqZn119qDOq0Pr91rb+pZLZdEHWZqX4Krvm/iEgMIqAn51gHZDd+ZK+srBW 5UrQuhsQfxmLVqGLkg6OaCm2Ypzhxxo1rp6jQsgk= Message-ID: <7edcf2a8-0dc4-456d-98c8-730ade633df5@arm.com> Date: Tue, 29 Sep 2026 14:35:07 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RESEND 0/9] selftests/mm: improve mremap_test To: "David Hildenbrand (Arm)" , Kalesh Singh Cc: Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , John Hubbard , Anshuman Khandual , Park Tae-sun , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260924050009.19974-1-sarthak.sharma@arm.com> <92ec3966-e68c-4dda-9d8b-9462f22c9e93@kernel.org> Content-Language: en-US From: Sarthak Sharma In-Reply-To: <92ec3966-e68c-4dda-9d8b-9462f22c9e93@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Kalesh and David! On 9/29/26 1:17 PM, David Hildenbrand (Arm) wrote: > On 9/29/26 09:32, Kalesh Singh wrote: >> On Mon, Sep 28, 2026 at 10:54 PM Sarthak Sharma wrote: >>> >>> >>> >>> On 9/24/26 10:30 AM, Sarthak Sharma wrote: >>>> This series fixes several correctness issues in mremap_test and >>>> simplifies and strengthens its data validation. >>>> >>>> Patch 1 converts the mremap_test to use kselftest helpers, removes >>>> manual tracking of failed tests and corrects some spelling errors. >>>> >>>> Patches 2 to 5 fix userfaultfd skipping, unexpected mremap success >>>> handling, multi-VMA data validation and failure reporting when data >>>> corruption is detected. >>>> >>>> Patch 6 removes the randomization and uses a simple pattern based approach. >>>> >>>> Patch 7 removes perf tests and timing infrastructure. >>>> >>>> Patch 8 removes validation threshold and always validates complete mappings. >>>> >>>> Patch 9 strengthens the multi VMA validation by also checking the >>>> mapping state of holes after remapping. >>> >>> Hello everyone! Just wanted to check if someone has had a chance to look >>> at the series. >>> >>> Also, Sashiko has a concern [1], and I had the same while posting the >>> series. I hope I can get some opinion from the community. >>> >>> Currently, for PUD remap tests, we allocate a source mapping of 2GB. We >>> only fault in the first threshold_mb amount of memory, remap the whole >>> region, and validate the already faulted threshold_mb amount of memory, >>> which is, by default, equal to 4MB and can be changed by the user by >>> supplying a command line option. >>> >>> Since we plan to remove all command line options from teh selftests, I >>> removed threshold_mb altogether, following some discussion on the list >>> [2]. This would now cause a 2GB source mapping, and its contents copied >>> from another 2GB buffer. This causes the process to have a 4GB RSS. > > Yeah, that's a lot for small CI systems indeed. > >>> Sashiko says that this can cause OOM killing in small CI machines. >>> >>> Would it be okay to keep a 4GB RSS in this case, or should we find some >>> other way of validating a part of the whole range instead? >> >> Hi Sarthak, >> >> IIRC when I initially introduced the test, John was concerned that >> validating the whole range would significantly increase the duration >> of the mm selftests; this is why the threshold was introduced. Please >> check how much it increases if we validate the full range (with >> David's suggestions) and if it's no longer a concern from other folks. >> I am fine with removing the threshold. I tested on an Orion O6. Here's the difference before and after removing the threshold right now. Before: 0.02user 0.07system 0:00.10elapsed 98%CPU (0avgtext+0avgdata 87332maxresident)k 0inputs+0outputs (0major+21133minor)pagefaults 0swaps After: 1.67user 4.91system 0:06.63elapsed 99%CPU (0avgtext+0avgdata 4195564maxresident)k 0inputs+0outputs (0major+2225058minor)pagefaults 0swaps I think instead of the time taken, the more concerning thing here is RSS (85MB vs 4GB). > > As discussed off-list, I guess it makes more sense to validate a couple of pages > at the beginning, the middle and the end? Yup, makes sense. I will implement this then.