From 43e9d1943278e96150b449ea1fa81f4ae27729d5 Mon Sep 17 00:00:00 2001 From: Wei Liu Date: Mon, 26 Aug 2013 12:59:37 +0100 Subject: [PATCH] xen-netback: remove page tracking facility The data flow from DomU to DomU on the same host in current copying scheme with tracking facility: copy DomU --------> Dom0 DomU | ^ |____________________________| copy The page in Dom0 is a page with valid MFN. So we can always copy from page Dom0, thus removing the need for a tracking facility. copy copy DomU --------> Dom0 -------> DomU Simple iperf test shows no performance regression (obviously we copy twice either way): W/ tracking: ~5.3Gb/s W/o tracking: ~5.4Gb/s Signed-off-by: Wei Liu Acked-by: Ian Campbell Acked-by: Matt Wilson Signed-off-by: David S. Miller --- drivers/net/xen-netback/netback.c | 77 +-------------------------------------- 1 file changed, 2 insertions(+), 75 deletions(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 64828de..91f163d 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -95,21 +95,6 @@ struct netbk_rx_meta { #define MAX_BUFFER_OFFSET PAGE_SIZE -/* extra field used in struct page */ -union page_ext { - struct { -#if BITS_PER_LONG < 64 -#define IDX_WIDTH 8 -#define GROUP_WIDTH (BITS_PER_LONG - IDX_WIDTH) - unsigned int group:GROUP_WIDTH; - unsigned int idx:IDX_WIDTH; -#else - unsigned int group, idx; -#endif - } e; - void *mapping; -}; - struct xen_netbk { wait_queue_head_t wq; struct task_struct *task; @@ -214,45 +199,6 @@ static inline unsigned long idx_to_kaddr(struct xen_netbk *netbk, return (unsigned long)pfn_to_kaddr(idx_to_pfn(netbk, idx)); } -/* extra field used in struct page */ -static inline void set_page_ext(struct page *pg, struct xen_netbk *netbk, - unsigned int idx) -{ - unsigned int group = netbk - xen_netbk; - union page_ext ext = { .e = { .group = group + 1, .idx = idx } }; - - BUILD_BUG_ON(sizeof(ext) > sizeof(ext.mapping)); - pg->mapping = ext.mapping; -} - -static int get_page_ext(struct page *pg, - unsigned int *pgroup, unsigned int *pidx) -{ - union page_ext ext = { .mapping = pg->mapping }; - struct xen_netbk *netbk; - unsigned int group, idx; - - group = ext.e.group - 1; - - if (group < 0 || group >= xen_netbk_group_nr) - return 0; - - netbk = &xen_netbk[group]; - - idx = ext.e.idx; - - if ((idx < 0) || (idx >= MAX_PENDING_REQS)) - return 0; - - if (netbk->mmap_pages[idx] != pg) - return 0; - - *pgroup = group; - *pidx = idx; - - return 1; -} - /* * This is the amount of packet we copy rather than map, so that the * guest can't fiddle with the contents of the headers while we do @@ -453,12 +399,6 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, { struct gnttab_copy *copy_gop; struct netbk_rx_meta *meta; - /* - * These variables are used iff get_page_ext returns true, - * in which case they are guaranteed to be initialized. - */ - unsigned int uninitialized_var(group), uninitialized_var(idx); - int foreign = get_page_ext(page, &group, &idx); unsigned long bytes; /* Data must not cross a page boundary. */ @@ -494,20 +434,9 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb, copy_gop = npo->copy + npo->copy_prod++; copy_gop->flags = GNTCOPY_dest_gref; - if (foreign) { - struct xen_netbk *netbk = &xen_netbk[group]; - struct pending_tx_info *src_pend; + copy_gop->source.domid = DOMID_SELF; + copy_gop->source.u.gmfn = virt_to_mfn(page_address(page)); - src_pend = &netbk->pending_tx_info[idx]; - - copy_gop->source.domid = src_pend->vif->domid; - copy_gop->source.u.ref = src_pend->req.gref; - copy_gop->flags |= GNTCOPY_source_gref; - } else { - void *vaddr = page_address(page); - copy_gop->source.domid = DOMID_SELF; - copy_gop->source.u.gmfn = virt_to_mfn(vaddr); - } copy_gop->source.offset = offset; copy_gop->dest.domid = vif->domid; @@ -1047,7 +976,6 @@ static struct page *xen_netbk_alloc_page(struct xen_netbk *netbk, page = alloc_page(GFP_KERNEL|__GFP_COLD); if (!page) return NULL; - set_page_ext(page, netbk, pending_idx); netbk->mmap_pages[pending_idx] = page; return page; } @@ -1155,7 +1083,6 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk, first->req.offset = 0; first->req.size = dst_offset; first->head = start_idx; - set_page_ext(page, netbk, head_idx); netbk->mmap_pages[head_idx] = page; frag_set_pending_idx(&frags[shinfo->nr_frags], head_idx); } -- 2.7.4