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[209.85.167.46]) by smtp.gmail.com with ESMTPSA id g22sm685654ljl.78.2020.11.21.10.23.29 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 21 Nov 2020 10:23:30 -0800 (PST) Received: by mail-lf1-f46.google.com with SMTP id a9so18133177lfh.2 for ; Sat, 21 Nov 2020 10:23:29 -0800 (PST) X-Received: by 2002:a19:ae06:: with SMTP id f6mr11146486lfc.133.1605983009454; Sat, 21 Nov 2020 10:23:29 -0800 (PST) MIME-Version: 1.0 References: <160596800145.154728.7192318545120181269.stgit@warthog.procyon.org.uk> In-Reply-To: <160596800145.154728.7192318545120181269.stgit@warthog.procyon.org.uk> From: Linus Torvalds Date: Sat, 21 Nov 2020 10:23:13 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 00/29] RFC: iov_iter: Switch to using an ops table To: David Howells Cc: Pavel Begunkov , Matthew Wilcox , Jens Axboe , Alexander Viro , linux-fsdevel , linux-block , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Nov 21, 2020 at 6:13 AM David Howells wrote: > > Can someone recommend a good way to benchmark this properly? The problem > is that the difference this makes relative to the amount of time taken to > actually do I/O is tiny. Maybe try /dev/zero -> /dev/null to try a load where the IO itself is cheap. Or vmsplice to /dev/null? Linus