linux-kernel - Re: [PATCH] rpmsg: compute number of buffers to allocate from vrings

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Date:	Wed, 13 Aug 2014 16:40:50 +0300
From:	Ohad Ben-Cohen <ohad@...ery.com>
To:	Suman Anna <s-anna@...com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] rpmsg: compute number of buffers to allocate from vrings

Hi Suman,

On Tue, Aug 12, 2014 at 7:19 PM, Suman Anna <s-anna@...com> wrote:
> Yes, I was playing around with using less buffers in the remoteproc
> resource table for the vrings. The remoteproc virtio code creates the
> vrings using the number of buffers based on .num field value of struct
> fw_rsc_vdev_vring in the resource table. The virtio rpmsg probe code
> though tries to set up the receive buffers for the same virtqueue based
> on the current hard-coded value of 512 buffers and virtqueue_add_inbuf
> would fail as the virtqueue is created with less number of buffers and
> throws a WARN_ON.

Gotcha - thanks for the details.

Limiting the number of buffers in case the vrings are too small makes
sense, but let's use RPMSG_NUM_BUFS as an upper bound, so wacky
resource tables won't trigger unreasonable memory waste.

Something in the lines of:

vrp->num_bufs = min(PMSG_NUM_BUFS, virtqueue_get_vring_size(vrp->rvq) * 2);

Should probably do the trick.

Does this satisfy your requirement?

Thanks,
Ohad.
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