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b=mvg+vmuIG/jTPG4UCyUgkfFHDh ugV+xPvBnWpvFM1mHw+0B+aZxEQZp05WnjtDCN+pr1PqJfia/FJqutvDNuOFvdSzmuebxL3kRiv2C EL6teyyYt8zc3JUhjTYGGDiOiDPql0uRQCrQXr0wxP+qPE1mHDCs3hKxxNlSuGdVmlTf0ewZ5m4k4 rahHLMQ9BAFqR8Ilkj9qisQc0xnwHAptHghYva38JA1mo67KzKUfbpTQ73ZaS2sb9a6T/YTnhfRIr DvEiwhbSFw99LU4OHk5hodhyy3Qc2MCCcMoYhQmhrRqKheMVMCVZ5gp7pzaF9tErH3Sy60ZPiZq78 BPB6fMfA==; Received: from [179.118.191.12] (helo=[192.168.15.100]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1wT0Lx-009x9D-V5; Fri, 29 May 2026 18:46:34 +0200 Message-ID: <6a58fd9c-1a69-403d-ad13-32bddea666f3@igalia.com> Date: Fri, 29 May 2026 13:46:27 -0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/6] treewide: Replace memcpy(..., current->comm) with strscpy() To: David Laight , Steven Rostedt Cc: Peter Zijlstra , Juri Lelli , Vincent Guittot , Christian Brauner , Kees Cook , Shuah Khan , willy@infradead.org, mathieu.desnoyers@efficios.com, Linus Torvalds , akpm@linux-foundation.org, Yafang Shao , andrii.nakryiko@gmail.com, arnaldo.melo@gmail.com, Petr Mladek , linux-kernel@vger.kernel.org, kernel-dev@igalia.com, linux-mm@kvack.org, linux-api@vger.kernel.org References: <20260524-tonyk-long_name-v2-0-332f6bd041c4@igalia.com> <20260524-tonyk-long_name-v2-3-332f6bd041c4@igalia.com> <20260526190625.3f4aca0a@gandalf.local.home> <20260527101842.376d567f@pumpkin> Content-Language: en-US From: =?UTF-8?Q?Andr=C3=A9_Almeida?= In-Reply-To: <20260527101842.376d567f@pumpkin> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: r8or5zg7yqabd7m8xfrcxk8yssdaacwy X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 2513C4000E X-HE-Tag: 1780073207-88695 X-HE-Meta: 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 AWbXq5ZT 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Em 27/05/2026 06:18, David Laight escreveu: > On Tue, 26 May 2026 19:06:25 -0400 > Steven Rostedt wrote: > >> On Sun, 24 May 2026 19:38:53 -0300 >> André Almeida wrote: >> >>> In order to increase the size of current->comm[] and to avoid breaking any >>> existing code, replace memcpy() with strscpy(). The later function makes >>> sure that the copy is NUL terminated. This is crucial given that the >>> source buffer might be larger than the destination buffer and could >>> truncate the NUL character out of it. > ... >> As tracing now slows it down by 3.9% which is a significant increase from 2.7% >> >> I really rather keep memcpy() here. Thanks Steve for taking the time for benchmarking this! > > I suspect the copies could/should be replaced by a copy_task_comm() > function that can perform optimisations that strscpy[_pad]() can't > do because it can (for example) assume that the source is terminated. > > When the src and dst are the same size it can also degenerate to > memcpy() - which should get inlined. > The cost of copying 64 bytes might still be rather more than copying > just 16. > A compromise of 32 may be better. > Ok, I will work on something like this for the v3.