netdev - Re: [EXT] [PATCH net-next 03/16] qlge: Deduplicate lbq_buf

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Message-ID: <CA+FuTSfKw6aaXk0hA0p_AUp9Oa_D+5Bwst8HUz7mJM-wO5Obow@mail.gmail.com>
Date:   Wed, 26 Jun 2019 11:42:06 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Benjamin Poirier <bpoirier@...e.com>
Cc:     Manish Chopra <manishc@...vell.com>,
        GR-Linux-NIC-Dev <GR-Linux-NIC-Dev@...vell.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [EXT] [PATCH net-next 03/16] qlge: Deduplicate lbq_buf_size

On Wed, Jun 26, 2019 at 7:37 AM Benjamin Poirier <bpoirier@...e.com> wrote:
>
> On 2019/06/26 09:24, Manish Chopra wrote:
> > > -----Original Message-----
> > > From: Benjamin Poirier <bpoirier@...e.com>
> > > Sent: Monday, June 17, 2019 1:19 PM
> > > To: Manish Chopra <manishc@...vell.com>; GR-Linux-NIC-Dev <GR-Linux-
> > > NIC-Dev@...vell.com>; netdev@...r.kernel.org
> > > Subject: [EXT] [PATCH net-next 03/16] qlge: Deduplicate lbq_buf_size
> > >
> > > External Email
> > >
> > > ----------------------------------------------------------------------
> > > lbq_buf_size is duplicated to every rx_ring structure whereas lbq_buf_order is
> > > present once in the ql_adapter structure. All rings use the same buf size, keep
> > > only one copy of it. Also factor out the calculation of lbq_buf_size instead of
> > > having two copies.
> > >
> > > Signed-off-by: Benjamin Poirier <bpoirier@...e.com>
> > > ---
> [...]
> >
> > Not sure if this change is really required, I think fields relevant to rx_ring should be present in the rx_ring structure.
> > There are various other fields like "lbq_len" and "lbq_size" which would be same for all rx rings but still under the relevant rx_ring structure.

The one argument against deduplicating might be if the original fields
are in a hot cacheline and the new location adds a cacheline access to
a hot path. Not sure if that is relevant here. But maybe something to
double check.