netdev - Re: [PATCH] inetpeer: reduce stack usage

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Message-Id: <20110412235126.63841dfe.shimoda.hiroaki@gmail.com>
Date:	Tue, 12 Apr 2011 23:51:26 +0900
From:	Hiroaki SHIMODA <shimoda.hiroaki@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>
Cc:	Scot Doyle <lkml@...tdoyle.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	netdev@...r.kernel.org
Subject: Re: [PATCH] inetpeer: reduce stack usage

On Tue, 12 Apr 2011 10:39:40 +0200
Eric Dumazet <eric.dumazet@...il.com> wrote:

> On 64bit arches, we use 752 bytes of stack when cleanup_once() is called
> from inet_getpeer().
> 
> Lets share the avl stack to save ~376 bytes.
> 
> Before patch :
> 
> # objdump -d net/ipv4/inetpeer.o | scripts/checkstack.pl
> 
> 0x000006c3 unlink_from_pool [inetpeer.o]:		376
> 0x00000721 unlink_from_pool [inetpeer.o]:		376
> 0x00000cb1 inet_getpeer [inetpeer.o]:			376
> 0x00000e6d inet_getpeer [inetpeer.o]:			376
> 0x0004 inet_initpeers [inetpeer.o]:			112
> # size net/ipv4/inetpeer.o
>    text	   data	    bss	    dec	    hex	filename
>    5320	    432	     21	   5773	   168d	net/ipv4/inetpeer.o
> 
> After patch :
> 
> objdump -d net/ipv4/inetpeer.o | scripts/checkstack.pl 
> 0x00000c11 inet_getpeer [inetpeer.o]:			376
> 0x00000dcd inet_getpeer [inetpeer.o]:			376
> 0x00000ab9 peer_check_expire [inetpeer.o]:		328
> 0x00000b7f peer_check_expire [inetpeer.o]:		328
> 0x0004 inet_initpeers [inetpeer.o]:			112
> # size net/ipv4/inetpeer.o
>    text	   data	    bss	    dec	    hex	filename
>    5163	    432	     21	   5616	   15f0	net/ipv4/inetpeer.o
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> Cc: Scot Doyle <lkml@...tdoyle.com>
> Cc: Stephen Hemminger <shemminger@...tta.com>
> Cc: Hiroaki SHIMODA <shimoda.hiroaki@...il.com>

I couldn't understand that actually cleanup_once() was called
from inet_getpeer() and then the stack overflow was hit,
but this patch surely reduces stack usage.

Reviewed-by: Hiroaki SHIMODA <shimoda.hiroaki@...il.com>

Thanks.
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