[lkml]   [2013]   [Oct]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [Xen-devel] [PATCH net-next RFC 1/5] xen-netback: Introduce TX grant map definitions
On 30/10/13 09:28, Jan Beulich wrote:
>>>> On 30.10.13 at 01:50, Zoltan Kiss <> wrote:
>> @@ -119,13 +126,22 @@ struct xenvif {
>> pending_ring_idx_t pending_cons;
>> u16 pending_ring[MAX_PENDING_REQS];
>> struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
>> + grant_handle_t grant_tx_handle[MAX_PENDING_REQS];
>> /* Coalescing tx requests before copying makes number of grant
>> * copy ops greater or equal to number of slots required. In
>> * worst case a tx request consumes 2 gnttab_copy.
>> */
>> struct gnttab_copy tx_copy_ops[2*MAX_PENDING_REQS];
>> + struct gnttab_unmap_grant_ref tx_unmap_ops[MAX_PENDING_REQS];
>> + struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
>> + /* passed to gnttab_[un]map_refs with pages under (un)mapping */
>> + struct page *pages_to_gnt[MAX_PENDING_REQS];
> I think you will want to try to limit the structure size here by putting
> things into unions that can't be used at the same time: Without
> having looked at the later patches yet, it seems quite unlikely that
> map and unmap can be used simultaneously. And the total of copy
> and map can't also be used at the same time, as for each pending
> request you would use either up to two copy slots or a single map
> slot. I didn't look for further opportunities of sharing space.

Indeed, map and unmap can't be done at the same time, so it's safe to
put them into union. But I'm afraid grant_tx_handle and pages_to_gnt
can't share space with other members.
tx_copy_ops is a different topic, let's discuss that in it's own thread ...



 \ /
  Last update: 2013-10-31 20:41    [W:0.123 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site