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Date:   Thu, 9 Jun 2022 20:58:33 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Sedat Dilek <sedat.dilek@gmail.com>
Cc:     Al Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org,
        Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>
Subject: Re: [RFC][PATCHES] iov_iter stuff
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On Thu, Jun 09, 2022 at 08:22:09PM +0100, Matthew Wilcox wrote:
> It's not really that.  This is more about per-IO overhead, so you'd want
> to do a lot of 1-byte writes to maximise your chance of seeing a
> difference.

Here's an earlier thread on ->read_iter vs ->read performance costs:

https://lore.kernel.org/linux-fsdevel/20210107151125.GB5270@casper.infradead.org/