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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Mdp3GqyOMVjYlN0r28tMkDTgkwOFuC9SrcWUedotlxK3zLLM03/skZBkZdiQojFeN dSrREtJUafgYqbCT/Go2OER5USAVJLBHaFRmekq7tT1j2W3xLrH/dreSqGRNr2jtOv 0C2TRa8vcymaJM3PMCgAGgrLcqKIPBVusR5D+TWk= Message-ID: <806952ab-8461-41eb-b7c7-7c8be56bd7c9@arm.com> Date: Tue, 14 Apr 2026 17:23:09 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests/mm: Simplify byte pattern checking in mremap_test To: "David Hildenbrand (Arm)" , akpm@linux-foundation.org, shuah@kernel.org Cc: ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, Sarthak Sharma References: <20260410143031.148173-1-dev.jain@arm.com> <5297e0da-d8ec-49df-9b32-0d9f907588d6@kernel.org> <8b5544eb-5ec0-4c85-a2da-7a454fa606dc@arm.com> <134c372e-5c9e-493d-b954-d9954546beaf@kernel.org> Content-Language: en-US From: Dev Jain In-Reply-To: <134c372e-5c9e-493d-b954-d9954546beaf@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 6456D4000C X-Stat-Signature: rhqyjix7jh9rryhzn9amqjsywaunazaj X-Rspamd-Server: rspam06 X-HE-Tag: 1776167598-211617 X-HE-Meta: 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 nsC+HWzD SborLgoi2vR9nR/ayay6aVFHweBt30au26ddCbivwNT5oBnlHgFiwqDbK9huucKXNLeMJNgKed/pbNhiSuZynKe0WVrmRhivNCtrVs9i5xGw132S2AiMEnAXqrOD7krem2Lsbt0jNkhk7wPRHQVGROlGXSoCmKWVf8YDFAxHKnoGZtDuKI+C/pzKejoWHOV3oaVa6lxx9MwLONjcwQnrnkhksRchbo9/OhUPzikyIMODLqgSJbxSSHBjX5aw7tMLXY4BmvITVigSKrpM+JwVpIMniVx5XxMut0MyK Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > > I would suggest to rewrite/simplify/clarify the patch description, not > talking about "buggy" etc, focusing on the simplification. > > " > The original version of mremap_test (7df666253f26: "kselftests: vm: add > mremap tests") validated remapped contents byte-by-byte and printed a > mismatch index in case the bytes streams didn't match. That was rather > inefficient, especially also if the test passed. > > Later, commit 7033c6cc9620 ("selftests/mm: mremap_test: optimize > execution time from minutes to seconds using chunkwise memcmp") used > memcmp() on bigger chunks, to fallback to byte-wise scanning to detect > the problematic index only if it discovered a problem. > > However, the implementation is overly complicated (e.g., get_sqrt() is > currently not optimal) and we don't really have to report the exact > index: whoever debugs the failing test can figure that out. > > Let's simplify by just comparing both byte streams with memcmp() and not > detecting the exact failed index. Thanks, I'll use this! > " > >