From f62805f1f30a40e354bd036b4cb799863a39be4b Mon Sep 17 00:00:00 2001 From: Stefano Stabellini Date: Tue, 24 Apr 2012 11:55:43 +0100 Subject: xen: enter/exit lazy_mmu_mode around m2p_override calls This patch is a significant performance improvement for the m2p_override: about 6% using the gntdev device. Each m2p_add/remove_override call issues a MULTI_grant_table_op and a __flush_tlb_single if kmap_op != NULL. Batching all the calls together is a great performance benefit because it means issuing one hypercall total rather than two hypercall per page. If paravirt_lazy_mode is set PARAVIRT_LAZY_MMU, all these calls are going to be batched together, otherwise they are issued one at a time. Adding arch_enter_lazy_mmu_mode/arch_leave_lazy_mmu_mode around the m2p_add/remove_override calls forces paravirt_lazy_mode to PARAVIRT_LAZY_MMU, therefore makes sure that they are always batched. However it is not safe to call arch_enter_lazy_mmu_mode if we are in interrupt context or if we are already in PARAVIRT_LAZY_MMU mode, so check for both conditions before doing so. Changes in v4: - rebased on 3.4-rc4: all the m2p_override users call gnttab_unmap_refs and gnttab_map_refs; - check whether we are in interrupt context and the lazy_mode we are in before calling arch_enter/leave_lazy_mmu_mode. Changes in v3: - do not call arch_enter/leave_lazy_mmu_mode in xen_blkbk_unmap, that can be called in interrupt context. Signed-off-by: Stefano Stabellini [v5: s/int lazy/bool lazy/] Signed-off-by: Konrad Rzeszutek Wilk --- drivers/xen/grant-table.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'drivers/xen') diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index 9f514bb561af..487e468f9ded 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -38,6 +38,7 @@ #include #include #include +#include #include #include @@ -827,6 +828,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops, struct page **pages, unsigned int count) { int i, ret; + bool lazy = false; pte_t *pte; unsigned long mfn; @@ -837,6 +839,11 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops, if (xen_feature(XENFEAT_auto_translated_physmap)) return ret; + if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) { + arch_enter_lazy_mmu_mode(); + lazy = true; + } + for (i = 0; i < count; i++) { /* Do not add to override if the map failed. */ if (map_ops[i].status) @@ -855,6 +862,9 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops, return ret; } + if (lazy) + arch_leave_lazy_mmu_mode(); + return ret; } EXPORT_SYMBOL_GPL(gnttab_map_refs); @@ -863,6 +873,7 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops, struct page **pages, unsigned int count, bool clear_pte) { int i, ret; + bool lazy = false; ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count); if (ret) @@ -871,12 +882,20 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops, if (xen_feature(XENFEAT_auto_translated_physmap)) return ret; + if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) { + arch_enter_lazy_mmu_mode(); + lazy = true; + } + for (i = 0; i < count; i++) { ret = m2p_remove_override(pages[i], clear_pte); if (ret) return ret; } + if (lazy) + arch_leave_lazy_mmu_mode(); + return ret; } EXPORT_SYMBOL_GPL(gnttab_unmap_refs); -- cgit v1.2.3