Re: [PATCH] xfs: optimise xfs_mod_icount/ifree when delta < 0

[Christoph Hellwig]

On Mon, Nov 04, 2019 at 07:29:40PM +0800, Shaokun Zhang wrote:
> From: Yang Guo <guoyang2@xxxxxxxxxx>
> 
> percpu_counter_compare will be called by xfs_mod_icount/ifree to check
> whether the counter less than 0 and it is a expensive function.
> let's check it only when delta < 0, it will be good for xfs's performance.

How much overhead do you see?  In the end the compare is just a debug
check, so if it actually shows up we should remove it entirely.