Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: glKYYngS4gBMZB3UT+dLcIaXda0XGE+bbXwfPd9cBXZ7b+jdmwGvPnK5NtrkkQ2DSe6hC3+Wcz
 sM6EKWU9ZYHQ==
IronPort-SDR: 7JEfHbJjz8l1Prs3sKYe2V/Wc9/rtE0D5/VqJqvsvM7T71U9JDnnqyZuOtN0i3hIBOGCoV49lg
 Tj9eFz/xJ1zw==
Date:   Fri, 12 Mar 2021 07:36:46 -0800
From:   Ira Weiny <ira.weiny@intel.com>
To:     Christoph Hellwig <hch@lst.de>
Cc:     Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org
Subject: Re: kmap_local semantics
Message-ID: <20210312153646.GE3014244@iweiny-DESK2.sc.intel.com>
References: <20210312065413.GA29805@lst.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20210312065413.GA29805@lst.de>
User-Agent: Mutt/1.11.1 (2018-12-01)
Precedence: bulk

On Fri, Mar 12, 2021 at 07:54:13AM +0100, Christoph Hellwig wrote:
> So with the new kmap_local interface is it possible / advisable to
> use local kmaps over code that might schedule(), e.g. to wait for I/O?

It is possible yes.  "Advisable" I think so.  Thomas knows better than I what
performance would be.

FWIW I have been working on converting kmaps to kmap_local.  Most of the
instances don't schedule AFAICT.

What I really don't want to see is any kmap'ings handed to another thread.  I
am working hard to eliminate the use of kmap for that use.  Is that going to be
a problem?

Ira