linux-kernel - RE: [RFC PATCH 9/9] iov_iter: Add benchmarking kunit tests for UBUF/IOVEC

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Date:   Fri, 15 Sep 2023 07:09:12 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'David Howells' <dhowells@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
CC:     Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
        "Christian Brauner" <christian@...uner.io>,
        Matthew Wilcox <willy@...radead.org>,
        "Brendan Higgins" <brendanhiggins@...gle.com>,
        David Gow <davidgow@...gle.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "kunit-dev@...glegroups.com" <kunit-dev@...glegroups.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christian Brauner <brauner@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: RE: [RFC PATCH 9/9] iov_iter: Add benchmarking kunit tests for
 UBUF/IOVEC

From: David Howells
> Sent: 14 September 2023 23:15
> 
> Add kunit tests to benchmark 256MiB copies to a UBUF iterator and an IOVEC
> iterator.  This attaches a userspace VM with a mapped file in it
> temporarily to the test thread.

Isn't that going to be completely dominated by the cache fills
from memory?

I'd have thought you'd need to use something with a lot of
small fragments so that the iteration code dominates the copy.

Some measurements can be made using readv() and writev()
on /dev/zero and /dev/null.

	David

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