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author | Stefano Stabellini <Stefano.Stabellini@eu.citrix.com> | 2012-04-24 11:55:43 +0100 |
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committer | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2012-05-07 15:33:19 -0400 |
commit | f62805f1f30a40e354bd036b4cb799863a39be4b (patch) | |
tree | 8b2005ae7c4ba79c7b711a33da3b571d1f8c225e /drivers/xen/grant-table.c | |
parent | 211063dc159695bd6072c5393e9bc729481c6ede (diff) | |
download | lwn-f62805f1f30a40e354bd036b4cb799863a39be4b.tar.gz lwn-f62805f1f30a40e354bd036b4cb799863a39be4b.zip |
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 <stefano.stabellini@eu.citrix.com>
[v5: s/int lazy/bool lazy/]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/xen/grant-table.c')
-rw-r--r-- | drivers/xen/grant-table.c | 19 |
1 files changed, 19 insertions, 0 deletions
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 <linux/vmalloc.h> #include <linux/uaccess.h> #include <linux/io.h> +#include <linux/hardirq.h> #include <xen/xen.h> #include <xen/interface/xen.h> @@ -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); |