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Date:   Wed, 17 Nov 2021 09:23:07 +0100
Message-Id: <CFRWRP3RTFT4.3VWRBA26OUSND@taiga>
Cc:     "Ammar Faizi" <ammarfaizi2@gnuweeb.org>,
        <linux-kernel@vger.kernel.org>, <linux-api@vger.kernel.org>,
        "io_uring Mailing List" <io-uring@vger.kernel.org>,
        "Jens Axboe" <axboe@kernel.dk>,
        "Pavel Begunkov" <asml.silence@gmail.com>, <linux-mm@kvack.org>
Subject: Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB
From:   "Drew DeVault" <sir@cmpwn.com>
To:     "Andrew Morton" <akpm@linux-foundation.org>
References: <20211028080813.15966-1-sir@cmpwn.com>
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 <593aea3b-e4a4-65ce-0eda-cb3885ff81cd@gnuweeb.org>
 <20211115203530.62ff33fdae14927b48ef6e5f@linux-foundation.org>
 <CFQZSHV700KV.18Y62SACP8KOO@taiga>
 <20211116114727.601021d0763be1f1efe2a6f9@linux-foundation.org>
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 <20211116133750.0f625f73a1e4843daf13b8f7@linux-foundation.org>
In-Reply-To: <20211116133750.0f625f73a1e4843daf13b8f7@linux-foundation.org>
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On Tue Nov 16, 2021 at 10:37 PM CET, Andrew Morton wrote:
> We're never going to get this right, are we? The only person who can
> decide on a system's appropriate setting is the operator of that
> system. Haphazardly increasing the limit every few years mainly
> reduces incentive for people to get this right.
>
> And people who test their software on 5.17 kernels will later find that
> it doesn't work on 5.16 and earlier, so they still need to tell their
> users to configure their systems appropriately. Until 5.16 is
> obsolete, by which time we're looking at increasing the default again.
>
> I don't see how this change gets us closer to the desired state:
> getting distros and their users to configure their systems
> appropriately.

Perfect is the enemy of good. This is a very simple change we can make
to improve the status quo, and I think that's worth doing. I do not have
time to develop a more sophisticated solution which steers the defaults
based on memory present, and I definitely don't have the time to
petition every distro to configure a better default for their particular
needs. This is the easiest way to get broad adoption for a better
default.