From: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>
Subject: Re: [PATCH] fs: pipe/sockets/anon dentries should not have a parent
Date: Fri, 21 Nov 2008 16:34:53 +0100
Message-ID: <20081121153453.GA23713@elte.hu>
References: <Pine.LNX.4.64.0811201727070.9089@quilx.com> <20081121083044.GL16242@elte.hu> <49267694.1030506@cosmosbay.com> <20081121.010508.40225532.davem@davemloft.net> <4926AEDB.10007@cosmosbay.com> <4926D022.5060008@cosmosbay.com> <20081121152148.GA20388@elte.hu> <4926D39D.9050603@cosmosbay.com>
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To: Eric Dumazet <dada1-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
Cc: David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>, cl-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, rjw-KKrjLPT3xs0@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, efault-Mmb7MZpHnFY@public.gmane.org, a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org, Linux Netdev List <netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>


* Eric Dumazet <dada1-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org> wrote:

> Ingo Molnar a =E9crit :
>> * Eric Dumazet <dada1-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org> wrote:
>>
>>> Before patch, time to run 8 millions of close(socket()) calls on 8 =
=20
>>> CPUS was :
>>>
>>> real    0m27.496s
>>> user    0m0.657s
>>> sys     3m39.092s
>>>
>>> After patch :
>>>
>>> real    0m23.997s
>>> user    0m0.682s
>>> sys     3m11.193s
>>
>> cool :-)
>>
>> What would it take to get it down to:
>>
>>>> Cost if run one one cpu :
>>>>
>>>> real    0m1.561s
>>>> user    0m0.092s
>>>> sys     0m1.469s
>>
>> i guess asking for a wall-clock cost of 1.561/8 would be too much? :=
)
>>
>
> It might be possible, depending on the level of hackery I am allowed=20
> to inject in fs/dcache.c and fs/inode.c :)

I think being able to open+close sockets in a scalable way is an=20
undisputed prime-time workload on Linux. The numbers you showed look=20
horrible.

Once you can show how much faster it could go via hacks, it should=20
only be a matter of time to achieve that safely and cleanly.

> wall cost of 1.56 (each cpu runs one loop of one million iterations)

(indeed.)

	Ingo