linux-kernel - Re: [PATCH v1 1/1] IB/hfi1: Don't cast parameter in bit operations

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Date:   Thu, 24 Feb 2022 03:00:59 +0200
From:   'Andy Shevchenko' <andriy.shevchenko@...ux.intel.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mike Marciniszyn <mike.marciniszyn@...nelisnetworks.com>,
        Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>
Subject: Re: [PATCH v1 1/1] IB/hfi1: Don't cast parameter in bit operations

On Wed, Feb 23, 2022 at 10:50:19PM +0000, David Laight wrote:
> From: 'Andy Shevchenko'
> > Sent: 23 February 2022 22:30
> > On Wed, Feb 23, 2022 at 09:44:32PM +0000, David Laight wrote:
> > > From: Andy Shevchenko
> > > > Sent: 23 February 2022 18:54

...

> > Either way it wastes cycles, the outcome depends on the actual distribution of
> > the interrupts across the bitmap. If it gathered closer to the beginning of the
> > bitmap, my code wins, otherwise the original ones.
> 
> The loop in bitmap_empty() will kill you - even if the first word in non-zero.

What loop? Did you really look into implementation of bitmap_empty()?

-- 
With Best Regards,
Andy Shevchenko