linux-kernel - Re: [PATCH v15 11/11] RFC: fw

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Message-ID: <20180228191553-mutt-send-email-mst@kernel.org>
Date:   Wed, 28 Feb 2018 19:16:35 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Marc-André Lureau <marcandre.lureau@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sergio Lopez Pascual <slp@...hat.com>,
        Baoquan He <bhe@...hat.com>, "Somlo, Gabriel" <somlo@....edu>,
        xiaolong.ye@...el.com
Subject: Re: [PATCH v15 11/11] RFC: fw_cfg: do DMA read operation

On Wed, Feb 28, 2018 at 05:00:58PM +0100, Marc-André Lureau wrote:
> Hi
> 
> On Wed, Feb 28, 2018 at 4:48 PM, Michael S. Tsirkin <mst@...hat.com> wrote:
> > On Wed, Feb 28, 2018 at 04:41:51PM +0100, Marc-André Lureau wrote:
> >> I don't know if it's always safe to enable dma in read_raw(), how
> >> could we know? Is there a check we could use to choose one or ther
> >> other (and thus avoiding explicit dma/readfn argument)?
> >
> > I'm not sure - but does it really matter? Is anyone reading large files
> > like this in production where speed matters?
> > Why even bother with DMA?
> 
> The difference is quite significante for not so small files, as shown above.
> 
> And if they access the fw_cfg entries at boot time, or when starting
> things etc, this may speed things up.

Question would be whether anyone at all does this.

-- 
MST