netdev - Re: [PATCH net-next v1 2/2] net/rds: Give each connection its own workqueue

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Message-ID: <0bee7457-eddc-493f-bdb9-a438347958f9@redhat.com>
Date: Tue, 4 Nov 2025 15:57:25 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Allison Henderson <achender@...nel.org>, netdev@...r.kernel.org
Cc: allison.henderson@...cle.com
Subject: Re: [PATCH net-next v1 2/2] net/rds: Give each connection its own
 workqueue

On 10/29/25 6:46 PM, Allison Henderson wrote:
> From: Allison Henderson <allison.henderson@...cle.com>
> 
> RDS was written to require ordered workqueues for "cp->cp_wq":
> Work is executed in the order scheduled, one item at a time.
> 
> If these workqueues are shared across connections,
> then work executed on behalf of one connection blocks work
> scheduled for a different and unrelated connection.
> 
> Luckily we don't need to share these workqueues.
> While it obviously makes sense to limit the number of
> workers (processes) that ought to be allocated on a system,
> a workqueue that doesn't have a rescue worker attached,
> has a tiny footprint compared to the connection as a whole:
> A workqueue costs ~800 bytes, while an RDS/IB connection
> totals ~5 MBytes.

Still a workqueue per connection feels overkill. Have you considered
moving to WQ_PERCPU for rds_wq? Why does not fit?

Thanks,

Paolo