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Date:   Tue, 30 Oct 2018 02:34:14 +0300
From:   Alexey Dobriyan <adobriyan@gmail.com>
To:     dancol@google.com
Cc:     linux-kernel@vger.kernel.org
Subject: Re: Re: [PATCH] fs/proc: introduce /proc/stat2 file
Message-ID: <20181029233414.GA29750@avx2>
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> I'd much rather move to a model in which userspace *explicitly* tells
> the kernel which fields it wants, with the kernel replying with just
> those particular fields, maybe in their raw binary representations.
> The ASCII-text bag-of-everything files would remain available for
> ad-hoc and non-performance critical use, but programs that cared about
> performance would have an efficient bypass. One concrete approach is
> to let users open up today's proc files and, instead of read(2)ing a
> text blob, use an ioctl to retrieve specified and targeted information
> of the sort that would normally be encoded in the text blob. Because
> callers would open the same file when using either the text or binary
> interfaces, little would have to change, and it'd be easy to implement
> fallbacks when a particular system doesn't support a particular
> fast-path ioctl.

You've just reinvented systems calls.

I suspect the DB in question cares about CPU related numbers and nothing
else which can be nicely split from the rest of /proc/stat.