linux-kernel - Re: ZONE_NORMAL memory exhausted by 4000 TCP sockets

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Date:	Mon, 6 Nov 2006 17:46:58 +0800
From:	"Zhao Xiaoming" <xiaoming.nj@...il.com>
To:	"Eric Dumazet" <dada1@...mosbay.com>
Cc:	linux-kernel@...r.kernel.org,
	"Linux Netdev List" <netdev@...r.kernel.org>
Subject: Re: ZONE_NORMAL memory exhausted by 4000 TCP sockets

2006/11/6, Eric Dumazet <dada1@...mosbay.com>:
> On Monday 06 November 2006 09:59, Zhao Xiaoming wrote:
>
> > Thank you again for your help. To have more detailed statistic data, I
> > did another round of test and gathered some data.  I give the overall
> > description here and detailed /proc/net/sockstat, /proc/meminfo,
> > /proc/slabinfo and /proc/buddyinfo follows.
> > =====================================================
> >                            slab mem cost        tcp mem pages       lowmem
> > free with traffic:             254668KB                 34693
> >       38772KB
> > without traffic:       104080KB                           1
> >        702652KB
> > =====================================================
>
> Thank you for detailed infos.
>
> It appears you have an extensive use of threads (about 10000), since :
>
> > task_struct        10095  10095   1360    3    1 : tunables   24   12
> >   8 : slabdata   3365   3365      0
>
> Each thread has a kernel stack, 8KB (ie 2 pages, order-1 allocation), plus a
> user vma
>
> > vm_area_struct     21346  21504     92   42    1 : tunables  120   60
> >   8 : slabdata    512    512      0
>
> Most likely you dont need that much threads. A program with fewer threads will
> perform better and use less ram.
>
>
Thanks for the comments. I known the threads may cost many memory.
However, I already excluded them from the statistics. The 'after test'
info was gotten while the 10000 threads running but no traffics
relayed. You may look at the meminfo of 'after test', there is still
104080 kB slab memory which should already included the thread kernel
memory cost (8K*10000=80MB). I know 10000 threads are not necessary
and just use the simple logic to do some test.
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