On 11/29/18 12:17 AM, Manjunath Patil wrote:
> Hi,
> Feel free to suggest/comment on this.
>
> I am trying to do the following at dst during the migration now.
> 1. Dont clear the old rinfo in blkif_free(). Instead just clean it.
> 2. Store the old rinfo and nr_rings into temp variables in negotiate_mq()
> 3. let nr_rings get re-calculated based on backend data
> 4. try allocating new memory based on new nr_rings
Since I suspect number of rings will likely be the same why not reuse
the rings in the common case?
> 5.
> a. If memory allocation is a success
> - free the old rinfo and proceed to use the new rinfo
> b. If memory allocation is a failure
> - use the old the rinfo
> - adjust the nr_rings to the lowest of new nr_rings and old nr_rings
> @@ -1918,10 +1936,24 @@ static int negotiate_mq(struct blkfront_info *info)
> sizeof(struct blkfront_ring_info),
> GFP_KERNEL);
> if (!info->rinfo) {
> - xenbus_dev_fatal(info->xbdev, -ENOMEM, "allocating ring_info
> structure");
> - info->nr_rings = 0;
> - return -ENOMEM;
> - }
> + if (unlikely(nr_rings_old)) {
> + /* We might waste some memory if
> + * info->nr_rings < nr_rings_old
> + */
> + info->rinfo = rinfo_old;
> + if (info->nr_rings > nr_rings_old)
> + info->nr_rings = nr_rings_old;
> + xenbus_dev_fatal(info->xbdev, -ENOMEM,
Why xenbus_dev_fatal()?
-boris
> + "reusing old ring_info structure(new ring size=%d)",
> + info->nr_rings);
> + } else {
> + xenbus_dev_fatal(info->xbdev, -ENOMEM,
> + "allocating ring_info structure");
> + info->nr_rings = 0;
> + return -ENOMEM;
> + }
> + } else if (unlikely(nr_rings_old))
> + kfree(rinfo_old);
>
> for (i = 0; i < info->nr_rings; i++) {
> struct blkfront_ring_info *rinfo;
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