[PATCH net-next] tcp/dccp: cache line align inet_hashinfo

[PATCH net-next] tcp/dccp: cache line align inet_hashinfo

[Eric Dumazet]

I have seen tcp_hashinfo starting at a non optimal location,
forcing input handlers to pull two cache lines instead of one,
and sharing a cache line that was dirtied more than necessary:

ffffffff83680600 b tcp_orphan_timer
ffffffff83680628 b tcp_orphan_cache
ffffffff8368062c b tcp_enable_tx_delay.__tcp_tx_delay_enabled
ffffffff83680630 B tcp_hashinfo
ffffffff83680680 b tcp_cong_list_lock

After this patch, ehash, ehash_locks, ehash_mask and ehash_locks_mask
are located in a read-only cache line.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/inet_hashtables.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index 99bd823e97f624e37cf3abb8ac0ec7eef4552b61..74399d20b2184945f2b39bf3dfedb3ae63b500f7 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -177,7 +177,7 @@ struct inet_hashinfo {
 	struct inet_listen_hashbucket	*lhash2;
 
 	bool				pernet;
-};
+} ____cacheline_aligned_in_smp;
 
 static inline struct inet_hashinfo *tcp_or_dccp_get_hashinfo(const struct sock *sk)
 {
-- 
2.41.0.640.ga95def55d0-goog

Re: [PATCH net-next] tcp/dccp: cache line align inet_hashinfo

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by David S. Miller <davem@davemloft.net>:

On Thu,  3 Aug 2023 07:53:34 +0000 you wrote:
> I have seen tcp_hashinfo starting at a non optimal location,
> forcing input handlers to pull two cache lines instead of one,
> and sharing a cache line that was dirtied more than necessary:
> 
> ffffffff83680600 b tcp_orphan_timer
> ffffffff83680628 b tcp_orphan_cache
> ffffffff8368062c b tcp_enable_tx_delay.__tcp_tx_delay_enabled
> ffffffff83680630 B tcp_hashinfo
> ffffffff83680680 b tcp_cong_list_lock
> 
> [...]

Here is the summary with links:
  - [net-next] tcp/dccp: cache line align inet_hashinfo
    https://git.kernel.org/netdev/net-next/c/6f5ca184cbef

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH net-next] tcp/dccp: cache line align inet_hashinfo

[Eric Dumazet]

On Fri, Aug 4, 2023 at 10:30 AM <patchwork-bot+netdevbpf@kernel.org> wrote:
>
> Hello:
>
> This patch was applied to netdev/net-next.git (main)
> by David S. Miller <davem@davemloft.net>:
>
> On Thu,  3 Aug 2023 07:53:34 +0000 you wrote:
> > I have seen tcp_hashinfo starting at a non optimal location,
> > forcing input handlers to pull two cache lines instead of one,
> > and sharing a cache line that was dirtied more than necessary:
> >
> > ffffffff83680600 b tcp_orphan_timer
> > ffffffff83680628 b tcp_orphan_cache
> > ffffffff8368062c b tcp_enable_tx_delay.__tcp_tx_delay_enabled
> > ffffffff83680630 B tcp_hashinfo
> > ffffffff83680680 b tcp_cong_list_lock
> >
> > [...]
>
> Here is the summary with links:
>   - [net-next] tcp/dccp: cache line align inet_hashinfo
>     https://git.kernel.org/netdev/net-next/c/6f5ca184cbef
>
> You are awesome, thank you!
> --
> Deet-doot-dot, I am a bot.
> https://korg.docs.kernel.org/patchwork/pwbot.html
>
>

Thanks !

Apparently this misalignment came with

commit cae3873c5b3a4fcd9706fb461ff4e91bdf1f0120
Author: Martin KaFai Lau <kafai@fb.com>
Date:   Wed May 11 17:06:05 2022 -0700

    net: inet: Retire port only listening_hash

Re: [PATCH net-next] tcp/dccp: cache line align inet_hashinfo

[Martin KaFai Lau]

On 8/4/23 1:33 PM, Eric Dumazet wrote:
> On Fri, Aug 4, 2023 at 10:30 AM <patchwork-bot+netdevbpf@kernel.org> wrote:
>>
>> Hello:
>>
>> This patch was applied to netdev/net-next.git (main)
>> by David S. Miller <davem@davemloft.net>:
>>
>> On Thu,  3 Aug 2023 07:53:34 +0000 you wrote:
>>> I have seen tcp_hashinfo starting at a non optimal location,
>>> forcing input handlers to pull two cache lines instead of one,
>>> and sharing a cache line that was dirtied more than necessary:
>>>
>>> ffffffff83680600 b tcp_orphan_timer
>>> ffffffff83680628 b tcp_orphan_cache
>>> ffffffff8368062c b tcp_enable_tx_delay.__tcp_tx_delay_enabled
>>> ffffffff83680630 B tcp_hashinfo
>>> ffffffff83680680 b tcp_cong_list_lock
>>>
>>> [...]
>>
>> Here is the summary with links:
>>    - [net-next] tcp/dccp: cache line align inet_hashinfo
>>      https://git.kernel.org/netdev/net-next/c/6f5ca184cbef
>>
>> You are awesome, thank you!
>> --
>> Deet-doot-dot, I am a bot.
>> https://korg.docs.kernel.org/patchwork/pwbot.html
>>
>>
> 
> Thanks !
> 
> Apparently this misalignment came with
> 
> commit cae3873c5b3a4fcd9706fb461ff4e91bdf1f0120
> Author: Martin KaFai Lau <kafai@fb.com>
> Date:   Wed May 11 17:06:05 2022 -0700
> 
>      net: inet: Retire port only listening_hash

Ah. Thanks for the fix. TIL.