linux-kernel - Re: [PATCH 0/4] IB: decrease large contigous allocation

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Date:   Wed, 26 Sep 2018 11:06:55 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Jan Dakinevich <jan.dakinevich@...tuozzo.com>
Cc:     Doug Ledford <dledford@...hat.com>,
        Yishai Hadas <yishaih@...lanox.com>,
        Leon Romanovsky <leon@...nel.org>,
        Parav Pandit <parav@...lanox.com>,
        Mark Bloch <markb@...lanox.com>,
        Daniel Jurgens <danielj@...lanox.com>,
        Kees Cook <keescook@...omium.org>,
        Kamal Heib <kamalheib1@...il.com>,
        Bart Van Assche <bvanassche@....org>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        Denis Lunev <den@...tuozzo.com>,
        Konstantin Khorenko <khorenko@...tuozzo.com>
Subject: Re: [PATCH 0/4] IB: decrease large contigous allocation

On Wed, Sep 26, 2018 at 06:48:09PM +0300, Jan Dakinevich wrote:
> On Tue, 18 Sep 2018 08:46:23 -0600
> Jason Gunthorpe <jgg@...pe.ca> wrote:
> 
> > On Tue, Sep 18, 2018 at 04:03:42PM +0300, Jan Dakinevich wrote:
> > > The size of mlx4_ib_device became too large to be allocated as
> > > whole contigous block of memory. Currently it takes about 55K. On
> > > architecture with 4K page it means 3rd order.
> > > 
> > > This patch series makes an attempt to split mlx4_ib_device into
> > > several parts and allocate them with less expensive kvzalloc
> > 
> > Why split it up? Any reason not to just allocate the whole thing with
> > kvzalloc?
> > 
> 
> To allocate whole ib_device with kvmalloc I will need replace kzalloc()
> by kvzalloc() in ib_alloc_device() and then review allocation, to make
> sure that no one uses this memory for DMA.

I would be shocked if some driver was DMA'ing out of struct ib_device
memory..

Jason