[{"id":3676802,"web_url":"http://patchwork.ozlabs.org/comment/3676802/","msgid":"<90a889aa-f204-4ea8-8642-6752aa1955d8@app.fastmail.com>","date":"2026-04-13T14:46:30","subject":"Re: [patch 17/38] ext4: Replace get_cycles() usage with ktime_get()","submitter":{"id":30,"url":"http://patchwork.ozlabs.org/api/people/30/","name":"Arnd Bergmann","email":"arnd@arndb.de"},"content":"On Fri, Apr 10, 2026, at 14:19, Thomas Gleixner wrote:\n> get_cycles() is not guaranteed to be functional on all systems/platforms\n> and the values returned are unitless and not easy to map to something\n> useful.\n>\n> Use ktime_get() instead, which provides nanosecond timestamps and is\n> functional everywhere.\n>\n> This is part of a larger effort to limit get_cycles() usage to low level\n> architecture code.\n>\n> Signed-off-by: Thomas Gleixner \n> Cc: \"Theodore Ts'o\" \n> Cc: linux-ext4@vger.kernel.org\n\nI think this is technically an ABI chance, since the time\ndifference gets exported through procfs, but the new version\nis clearly the right thing to do since it replaces a hardware\nspecific value with a portable one.\n\n Arnd","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=arndb.de header.i=@arndb.de header.a=rsa-sha256\n header.s=fm1 header.b=LmjozJUZ;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=messagingengine.com header.i=@messagingengine.com\n header.a=rsa-sha256 header.s=fm2 header.b=P0Pt1FmZ;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; 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Donenfeld\" ,\n \"Richard Henderson\" ,\n linux-alpha@vger.kernel.org, \"Russell King\" ,\n linux-arm-kernel@lists.infradead.org,\n \"Catalin Marinas\" ,\n \"Huacai Chen\" , loongarch@lists.linux.dev,\n \"Geert Uytterhoeven\" ,\n linux-m68k@lists.linux-m68k.org, \"Dinh Nguyen\" ,\n \"Jonas Bonn\" ,\n \"linux-openrisc@vger.kernel.org\" ,\n \"Helge Deller\" , linux-parisc@vger.kernel.org,\n \"Michael Ellerman\" , linuxppc-dev@lists.ozlabs.org,\n \"Paul Walmsley\" , linux-riscv@lists.infradead.org,\n \"Heiko Carstens\" , linux-s390@vger.kernel.org,\n \"David S . Miller\" , sparclinux@vger.kernel.org","Message-Id":"<90a889aa-f204-4ea8-8642-6752aa1955d8@app.fastmail.com>","In-Reply-To":"<20260410120318.727211419@kernel.org>","References":"<20260410120044.031381086@kernel.org>\n <20260410120318.727211419@kernel.org>","Subject":"Re: [patch 17/38] ext4: Replace get_cycles() usage with ktime_get()","Content-Type":"text/plain","Content-Transfer-Encoding":"7bit","X-Spam-Status":"No, score=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tDKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"}}]