From: Stefano Stabellini Date: Tue, 24 Apr 2012 10:55:43 +0000 (+0100) Subject: xen: enter/exit lazy_mmu_mode around m2p_override calls X-Git-Tag: v3.5-rc1~89^2~6 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f62805f1;p=pandora-kernel.git 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 --- Reading git-diff-tree failed