Messages in this thread |  | | Date | Thu, 31 Oct 2013 19:22:27 +0000 | From | Zoltan Kiss <> | Subject | Re: [Xen-devel] [PATCH net-next RFC 1/5] xen-netback: Introduce TX grant map definitions |
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On 30/10/13 09:28, Jan Beulich wrote: >>>> On 30.10.13 at 01:50, Zoltan Kiss <zoltan.kiss@citrix.com> 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 ...
Thanks,
Zoli
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