netdev - Re: [PATCH v8 net-next 0/4] udp: Add 4-tuple hash for connected sockets

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Message-ID: <673245b18be9c_b4a05294bc@willemb.c.googlers.com.notmuch>
Date: Mon, 11 Nov 2024 12:58:09 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Philo Lu <lulie@...ux.alibaba.com>, 
 netdev@...r.kernel.org
Cc: willemdebruijn.kernel@...il.com, 
 davem@...emloft.net, 
 edumazet@...gle.com, 
 kuba@...nel.org, 
 pabeni@...hat.com, 
 dsahern@...nel.org, 
 horms@...nel.org, 
 antony.antony@...unet.com, 
 steffen.klassert@...unet.com, 
 linux-kernel@...r.kernel.org, 
 dust.li@...ux.alibaba.com, 
 jakub@...udflare.com, 
 fred.cc@...baba-inc.com, 
 yubing.qiuyubing@...baba-inc.com
Subject: Re: [PATCH v8 net-next 0/4] udp: Add 4-tuple hash for connected
 sockets

Philo Lu wrote:
> This patchset introduces 4-tuple hash for connected udp sockets, to make
> connected udp lookup faster.
> 
> Stress test results (with 1 cpu fully used) are shown below, in pps:
> (1) _un-connected_ socket as server
>     [a] w/o hash4: 1,825176
>     [b] w/  hash4: 1,831750 (+0.36%)
> 
> (2) 500 _connected_ sockets as server
>     [c] w/o hash4:   290860 (only 16% of [a])
>     [d] w/  hash4: 1,889658 (+3.1% compared with [b])
> With hash4, compute_score is skipped when lookup, so [d] is slightly
> better than [b].
> 
> Patch1: Add a new counter for hslot2 named hash4_cnt, to avoid cache line
>         miss when lookup.
> Patch2: Add hslot/hlist_nulls for 4-tuple hash.
> Patch3 and 4: Implement 4-tuple hash for ipv4 and ipv6.
> 
> The detailed motivation is described in Patch 3.
> 
> The 4-tuple hash increases the size of udp_sock and udp_hslot. Thus add it
> with CONFIG_BASE_SMALL, i.e., it's a no op with CONFIG_BASE_SMALL.
> 
> changelogs:
> v7 -> v8:
> - add EXPORT_SYMBOL for ipv6.ko build
> 
> v6 -> v7 (Kuniyuki Iwashima):
> - export udp_ehashfn to be used by udpv6 rehash
> 
> v5 -> v6 (Paolo Abeni):
> - move udp_table_hash4_init from patch2 to patch1
> - use hlist_nulls for lookup-rehash race
> - add test results in commit log
> - add more comment, e.g., for rehash4 used in hash4
> - add ipv6 support (Patch4), and refactor some functions for better
>   sharing, without functionality change
> 
> v4 -> v5 (Paolo Abeni):
> - add CONFIG_BASE_SMALL with which udp hash4 does nothing
> 
> v3 -> v4 (Willem de Bruijn):
> - fix mistakes in udp_pernet_table_alloc()
> 
> RFCv2 -> v3 (Gur Stavi):
> - minor fix in udp_hashslot2() and udp_table_init()
> - add rcu sync in rehash4()
> 
> RFCv1 -> RFCv2:
> - add a new struct for hslot2
> - remove the sockopt UDP_HASH4 because it has little side effect for
>   unconnected sockets
> - add rehash in connect()
> - re-organize the patch into 3 smaller ones
> - other minor fix
> 
> v7:
> https://lore.kernel.org/all/20241105121225.12513-1-lulie@linux.alibaba.com/
> v6:
> https://lore.kernel.org/all/20241031124550.20227-1-lulie@linux.alibaba.com/
> v5:
> https://lore.kernel.org/all/20241018114535.35712-1-lulie@linux.alibaba.com/
> v4:
> https://lore.kernel.org/all/20241012012918.70888-1-lulie@linux.alibaba.com/
> v3:
> https://lore.kernel.org/all/20241010090351.79698-1-lulie@linux.alibaba.com/
> RFCv2:
> https://lore.kernel.org/all/20240924110414.52618-1-lulie@linux.alibaba.com/
> RFCv1:
> https://lore.kernel.org/all/20240913100941.8565-1-lulie@linux.alibaba.com/
> 
> Philo Lu (4):
>   net/udp: Add a new struct for hash2 slot
>   net/udp: Add 4-tuple hash list basis
>   ipv4/udp: Add 4-tuple hash for connected socket
>   ipv6/udp: Add 4-tuple hash for connected socket
> 
>  include/linux/udp.h |  11 ++
>  include/net/udp.h   | 137 +++++++++++++++++++++++--
>  net/ipv4/udp.c      | 245 +++++++++++++++++++++++++++++++++++++++-----
>  net/ipv6/udp.c      | 117 +++++++++++++++++++--
>  4 files changed, 468 insertions(+), 42 deletions(-)

Acked-by: Willem de Bruijn <willemb@...gle.com>

My expertise in routing is limited, fair warning.
But I see no significant remaining issues.