netdev - Re: many sockets, slow sendto

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 21 Mar 2007 23:12:40 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Zacco <zacco@...hu>
CC:	David Miller <davem@...emloft.net>, baruch@...en.org,
	netdev@...r.kernel.org
Subject: Re: many sockets, slow sendto

Eric Dumazet a écrit :
> Currently, udp_hash[UDP_HTABLE_SIZE] is using a hash function based on 
> dport number only.
> 
> In your case, as you use a single port value, all sockets are in a 
> single slot of this hash table :
> To find the good socket, __udp4_lib_lookup() has to search in a list 
> with thousands of elements. Not that good, isnt it ? :(

In case you want to try, here is a patch that could help you :)

[PATCH] INET : IPV4 UDP lookups converted to a 2 pass algo

Some people want to have many UDP sockets, binded to a single port but many 
different addresses. We currently hash all those sockets into a single chain. 
Processing of incoming packets is very expensive, because the whole chain must 
be examined to find the best match.

I chose in this patch to hash UDP sockets with a hash function that take into 
account both their port number and address : This has a drawback because we 
need two lookups : one with a given address, one with a wildcard (null) address.

Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

View attachment "udp_2pass_lookups.patch" of type "text/plain" (7622 bytes)