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Date:      Fri, 14 Feb 2020 18:29:30 +0000
From:      Steve O'Hara-Smith <steve@sohara.org>
To:        Robert Huff <roberthuff@rcn.com>
Cc:        tech-lists <tech-lists@zyxst.net>, freebsd-questions@freebsd.org
Subject:   Re: some questions about disk partitioning and filesystems and booting
Message-ID:  <20200214182930.df325195e2a378a3b6f50573@sohara.org>
In-Reply-To: <24134.39022.519866.759080@jerusalem.litteratus.org>
References:  <20200213150229.GC14144@bastion.zyxst.net> <CAEJNuHxrVPfU_TB35AEXaq0QdM=p-v0rnuZWtmAgQdm_KRMNTw@mail.gmail.com> <20200213155256.GD14144@bastion.zyxst.net> <1090523a-377c-9412-5db1-38e825e35956@mm.st> <20200214121003.GB39057@bastion.zyxst.net> <24134.39022.519866.759080@jerusalem.litteratus.org>

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On Fri, 14 Feb 2020 07:54:06 -0500
Robert Huff <roberthuff@rcn.com> wrote:

> 	_If_ that's true, then it's a bug and needs to be fixed.  The
> folks posting here may not need it ... but I find it hard to imagine
> various organizations that use FreeBSD (or would like to) on hardcore
> server hardware wouldn't find that a substantial liability.
> 	While this may be more suited to hackers@: can anyone here
> confirm there is an encoded limit on swap space?

	According to this there is (or was at the time) a hard coded limit
of 32GB per swap device - just checked it's still there.

	You can of course have several swap devices - which is probably a
very good idea if you actually need more than 32GB of swap.

https://lists.freebsd.org/pipermail/freebsd-stable/2011-August/063529.html

	Relevant text:

Anyway, there is one thing in /usr/src/sys/vm/swap_pager.c (so if you get
this warning (reducing size to maximum of... per swap unit)), this might be
the reason:

        /*
         * If we go beyond this, we get overflows in the radix
         * tree bitmap code.
         */
        mblocks = 0x40000000 / BLIST_META_RADIX;
        if (nblks > mblocks) {
                printf("WARNING: reducing size to maximum of %lu blocks per
swap unit\n", mblocks);
                nblks = mblocks;
        }


-- 
Steve O'Hara-Smith <steve@sohara.org>



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