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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <20230914221526.3153402-1-dhowells@redhat.com> <20230914221526.3153402-10-dhowells@redhat.com> To: David Laight Cc: dhowells@redhat.com, Al Viro , Linus Torvalds , Jens Axboe , Christoph Hellwig , "Christian Brauner" , Matthew Wilcox , "Brendan Higgins" , David Gow , "linux-fsdevel@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-mm@kvack.org" , "netdev@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "kunit-dev@googlegroups.com" , "linux-kernel@vger.kernel.org" , Andrew Morton , Christian Brauner , David Hildenbrand , John Hubbard Subject: Re: [RFC PATCH 9/9] iov_iter: Add benchmarking kunit tests for UBUF/IOVEC MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3370514.1694772627.1@warthog.procyon.org.uk> Date: Fri, 15 Sep 2023 11:10:27 +0100 Message-ID: <3370515.1694772627@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Rspamd-Queue-Id: 994D810000F X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: p61p3djmmnc1gg4ybybicfkxy8o15qid X-HE-Tag: 1694772636-502106 X-HE-Meta: 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 ateUze5A eGkitB4h85zbCgi4w/uTIDQOnGbIJ13lfbVNtzfWAOo92MoL4lzOImgzxCtF83X8ct+eOxnS5mVlOQFv57uyYKD9b35Ye2NkwwC5+msmxUNzHrc6aUWChQlTnrLPavQ+mE+sFCWVhufcVe8gQeXgBeaeOQ1YPwfhHxhJKgupW6kuXXXy71i6is2RKhU+WRQ/hw5fGRXTUKBgqieY/AOCpBjiCRM6znsTMdKFglG6zQLw8CeIbFtjwYeNra3m/h2J+WAgwVFmsMOXqDiaFkKmt6zYXlkX++6/6tOYldY21EHUrkV4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: David Laight wrote: > > 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? Yes... but it should be consistent in the amount of time that consumes since no device drivers are involved. I can try adding the same folio to the anon_file multiple times - it might work especially if I don't put the pages on the LRU (if that's even possible) - but I wanted separate pages for the extraction test. > I'd have thought you'd need to use something with a lot of > small fragments so that the iteration code dominates the copy. That would actually be a separate benchmark case which I should try also. > Some measurements can be made using readv() and writev() > on /dev/zero and /dev/null. Forget /dev/null; that doesn't actually engage any iteration code. The same for writing to /dev/zero. Reading from /dev/zero does its own iteration thing rather than using iterate_and_advance(), presumably because it checks for signals and resched. David