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Date:      Sun, 11 Nov 2012 00:04:51 +0100
From:      Andre Oppermann <andre@freebsd.org>
To:        Alfred Perlstein <bright@mu.org>
Cc:        src-committers@freebsd.org, Eitan Adler <eadler@freebsd.org>, Peter Wemm <peter@wemm.org>, svn-src-all@freebsd.org, Alfred Perlstein <alfred@freebsd.org>, svn-src-head@freebsd.org
Subject:   Re: svn commit: r242847 - in head/sys: i386/include kern
Message-ID:  <509EDD93.3020001@freebsd.org>
In-Reply-To: <509ED439.8090607@mu.org>
References:  <201211100208.qAA28e0v004842@svn.freebsd.org> <CAF6rxg=HPmQS1T-LFsZ=DuKEqH30iJFpkz%2BJGhLr4OBL8nohjg@mail.gmail.com> <509DC25E.5030306@mu.org> <509E3162.5020702@FreeBSD.org> <509E7E7C.9000104@mu.org> <CAF6rxgmV8dx-gsQceQKuMQEsJ%2BGkExcKYxEvQ3kY%2B5_nSjvA3w@mail.gmail.com> <509E830D.5080006@mu.org> <509E847E.30509@mu.org> <CAF6rxgnfm4HURYp=O4MY8rB6H1tGiqJ3rdPx0rZ8Swko5mAOZg@mail.gmail.com> <509E8930.50800@mu.org> <CAF6rxgmabVuR0JoFURRUF%2Bed0hmT=LF_n5LXSip0ibU0hk6qWw@mail.gmail.com> <CAGE5yCouCWr4NKbgnjKfLcjc8EWqG0wRiSmXDDnrnM3%2BUc8KVQ@mail.gmail.com> <CAF6rxg=ryNEMEidJdgf8-Ab=bD15R1ypcz-bS8183U4JK_Q17g@mail.gmail.com> <CAGE5yCoeTXf7x4ZBDXnHJ4dnFi-_2R28kB8HxOB%2B=Je4aJGYQQ@mail.gmail.com> <509EA869.6030407@freebsd.org> <509ED439.8090607@mu.org>

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On 10.11.2012 23:24, Alfred Perlstein wrote:
> On 11/10/12 11:18 AM, Andre Oppermann wrote:
>> On 10.11.2012 19:04, Peter Wemm wrote:
>>> This is complicated but we need a simple user visible view of it.  It
>>> really needs to be something like "nmbclusters defaults to 6% of
>>> physical ram, with machine dependent limits".  The MD limits are bad
>>> enough, and using bogo-units like "maxusers" just makes it worse.
>>
>> Yes, that would be optimal.
>>
> No it would not.
>
> I used to be able to tell people "hey just try increasing maxusers" and they would and suddenly the
> box would be OK.
>
> Now I'll have to remember 3,4,5,10,20x tunable to increase?

No.  The whole mbuf and cluster stuff isn't allocated or reserved
at boot time.  We simply need a limit to prevent it from exhausting
all available kvm / physical memory whichever is less.

Other than that there is no relation to maxusers except historic
behavior.

So the ideal mbuf limit is just short of keeling the kernel over
no matter what maxusers says.  There also isn't much to tune then
as the only fix would be to add more physical ram.

-- 
Andre

> The concept of a single knob to do ***basic*** tuning is a good one.
>
> Please leave it alone.
>
> There is nothing about "maxusers" that stops someone from tuning individual subsystems.
>
> You just wind up making FreeBSD an "experts only" playground by gratuitously changing this.
>
> Again, please leave it alone, we need basic tuning to be simple and easy.
>
> What we have now works.  Do not pull it apart and make it convoluted and "expert only".
>
> thank you,
>
> -Alfred
>
>




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