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Re: [PATCH][RFC 3] cleaning up struct sock

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: Re: [PATCH][RFC 3] cleaning up struct sock
From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxx>
Date: Fri, 21 Dec 2001 11:54:38 -0200
Cc: SteveW@xxxxxxx, jschlst@xxxxxxxxx, ncorbic@xxxxxxxxxxx, eis@xxxxxxxxxxxxx, dag@xxxxxxxxxxx, torvalds@xxxxxxxxxxxxx, marcelo@xxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
In-reply-to: <20011220.002126.119272610.davem@xxxxxxxxxx>
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References: <20011218.130809.22018359.davem@xxxxxxxxxx> <20011218232222.A1963@xxxxxxxxxxxxxxxx> <20011220012339.A919@xxxxxxxxxxxxxxxx> <20011220.002126.119272610.davem@xxxxxxxxxx>
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Em Thu, Dec 20, 2001 at 12:21:26AM -0800, David S. Miller escreveu:
>    From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxx>
>    Date: Thu, 20 Dec 2001 01:23:39 -0200
> 
>    Available at:
>    
>    http://www.kernel.org/pub/linux/kernel/people/acme/v2.5/2.5.1/
>    sock.cleanup-2.5.1.patch.bz2
> 
> Looking pretty good.  I have one improvement.
> 
> I'd rather you pass the "kmem_cache_t" directly into sk_alloc, use
> NULL for "I don't have any extra private area".
> 
> And then, for the IP case lay it out like this:
> 
>       struct sock
>       struct ip_opt
>       struct {tcp,raw4,...}_opt
> 
> And use different kmem_cache_t's for each protocol instead of
> the same one for tcp, raw4, etc.
> 
> RAW/UDP sockets waste a lot of space with your current layout.

Indeed it wastes, but the current setup in the stock kernel wastes even more ;)

Well, did what you suggested, adding a slab parameter to sk_alloc and I
also overloaded zero_it but its current behaviour is maintained, i.e., 0 ==
don't zeroes the newly allocated sock, 1 == zeroes it, the overloading is:
1 == sizeof(struct sock), > 1 == objsize of the per protocol slabcache. For
now I did only to UDPv4 sockets, will do the others this afternoon, this is
the result so far:

[rama2 kernel-acme]$ grep sock /proc/slabinfo
unix_sock   7   20   400  1  2  1 :  17   572 2 0  0
udp_sock    6   10   372  1  1  1 :   7    31 1 0  0
tcp_sock   13   15   800  3  3  1 :  13    46 3 0  0
sock        0    0   336  0  0  1 :   0     0 0 0  0

Now UDP sockets use only 372 bytes while in the stock kernel it uses 1280
bytes when all the protocols are selected (as modules or statically
linked, but more than 1 KB when just TCP/IP v4 is selected).

More to come. Patch will be available later today.

- Arnaldo

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