linux-kernel - Re: [PATCH 5.15 042/136] ice: xsk: Force rings to be sized to power of 2

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Date:   Mon, 29 Aug 2022 13:39:13 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.15 042/136] ice: xsk: Force rings to be sized to power
 of 2

On Mon, Aug 29, 2022 at 01:16:40PM +0200, Maciej Fijalkowski wrote:
> On Mon, Aug 29, 2022 at 12:58:29PM +0200, Greg Kroah-Hartman wrote:
> > From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> > 
> > [ Upstream commit 296f13ff3854535009a185aaf8e3603266d39d94 ]
> > 
> > With the upcoming introduction of batching to XSK data path,
> > performance wise it will be the best to have the ring descriptor count
> > to be aligned to power of 2.
> > 
> > Check if ring sizes that user is going to attach the XSK socket fulfill
> > the condition above. For Tx side, although check is being done against
> > the Tx queue and in the end the socket will be attached to the XDP
> > queue, it is fine since XDP queues get the ring->count setting from Tx
> > queues.
> 
> Hi Greg,
> 
> We had multiple customers reporting that this change makes them unable to
> use max ring size which is 8160 for this particular driver (which is not a
> power of 2 obviously) so we are about to send a patch that will drop this
> limitation.
> 
> To avoid the double work, can you please not proceed with this one?
> The other two:
> ice: xsk: prohibit usage of non-balanced queue id
> ice: xsk: use Rx rings XDP ring when picking NAPI context
> 
> are valid and needed.

This is in the 5.18 kernel release, which has been out for a while.

We will be glad to pick up the fixed commit when it hits Linus's tree.

> FWIW this was a part of -next patch set, so I suppose you picked this due
> to some dependency?

I think it was, for a later patch in the series, 5a42f112d367 ("ice:
xsk: prohibit usage of non-balanced queue id").

thanks,

greg k-h