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

Arnaldo Carvalho de Melo (acme@conectiva.com.br)
Fri, 21 Dec 2001 11:54:38 -0200


Em Thu, Dec 20, 2001 at 12:21:26AM -0800, David S. Miller escreveu:
> From: Arnaldo Carvalho de Melo <acme@conectiva.com.br>
> 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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