Subject: Re: kdbus: to merge or not to merge?
To: Andy Lutomirski <luto@amacapital.net>
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Cc: David Herrmann <dh.herrmann@gmail.com>, Tom Gundersen <teg@jklm.no>,
        "Kalle A. Sandstrom" <ksandstr@iki.fi>,
        Greg KH <gregkh@linuxfoundation.org>, Borislav Petkov <bp@alien8.de>,
        One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        Havoc Pennington <havoc.pennington@gmail.com>,
        Djalal Harouni <tixxdz@opendz.org>, cee1 <fykcee1@gmail.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
From: Daniel Mack <daniel@zonque.org>
Message-ID: <55C4C35A.4070306@zonque.org>
Date: Fri, 7 Aug 2015 16:40:26 +0200
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On 08/06/2015 08:43 PM, Andy Lutomirski wrote:
> Nonetheless, it looks like the slice logic (aside: it looks *way* more
> complicated than necessary -- what's wrong with circular buffers)
> will, under most (but not all!) workloads, concentrate access to a
> smallish fraction of the pool.  This is IMO bad, since it means that
> most of the time most of the pool will remain uncommitted.  If, at
> some point, something causes the access pattern to change and hit all
> the pages (even just once), suddenly all of the pools get committed,
> and your memory usage blows up.

That's a general problem with memory overcommitment, and not specific to
kdbus. IOW: You'd have the same problem with a similar logic implemented
in userspace, right?


Daniel

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