netdev - Re: [PATCH net-next v6 1/4] eventpoll: support busy poll per epoll instance

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Message-ID: <20240207121124.12941ed9@kernel.org>
Date: Wed, 7 Feb 2024 12:11:24 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Joe Damato <jdamato@...tly.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 chuck.lever@...cle.com, jlayton@...nel.org, linux-api@...r.kernel.org,
 brauner@...nel.org, edumazet@...gle.com, davem@...emloft.net,
 alexander.duyck@...il.com, sridhar.samudrala@...el.com,
 willemdebruijn.kernel@...il.com, weiwan@...gle.com,
 David.Laight@...LAB.COM, arnd@...db.de, sdf@...gle.com,
 amritha.nambiar@...el.com, Alexander Viro <viro@...iv.linux.org.uk>, Jan
 Kara <jack@...e.cz>, "open list:FILESYSTEMS (VFS and infrastructure)"
 <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH net-next v6 1/4] eventpoll: support busy poll per epoll
 instance

On Wed, 7 Feb 2024 11:14:08 -0800 Joe Damato wrote:
> > Why do we need u64 for usecs? I think u16 would do, and u32 would give
> > a very solid "engineering margin". If it was discussed in previous
> > versions I think it's worth explaining in the commit message.  
> 
> In patch 4/4 the value is limited to U32_MAX, but if you prefer I use a u32
> here instead, I can make that change.

Unless you have a clear reason not to, I think using u32 would be more
natural? If my head math is right the range for u32 is 4096 sec,
slightly over an hour? I'd use u32 and limit it to S32_MAX.