From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752829Ab2DXKuI (ORCPT ); Tue, 24 Apr 2012 06:50:08 -0400 Received: from smtp.ctxuk.citrix.com ([62.200.22.115]:30685 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751854Ab2DXKuG (ORCPT ); Tue, 24 Apr 2012 06:50:06 -0400 X-IronPort-AV: E=Sophos;i="4.75,472,1330905600"; d="scan'208";a="12102636" Date: Tue, 24 Apr 2012 11:55:43 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball-desktop To: Konrad Rzeszutek Wilk CC: Stefano Stabellini , "xen-devel@lists.xensource.com" , "linux-kernel@vger.kernel.org" Subject: [PATCH v4] xen: enter/exit lazy_mmu_mode around m2p_override calls In-Reply-To: <20120417144318.GA28477@phenom.dumpdata.com> Message-ID: References: <1334075375-25442-1-git-send-email-stefano.stabellini@eu.citrix.com> <20120417130340.GA25593@phenom.dumpdata.com> <20120417144318.GA28477@phenom.dumpdata.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index e570c6f..a18a3e8 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -38,6 +38,7 @@ #include #include #include +#include #include #include @@ -826,7 +827,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops, struct gnttab_map_grant_ref *kmap_ops, struct page **pages, unsigned int count) { - int i, ret; + int i, ret, lazy = 0; pte_t *pte; unsigned long mfn; @@ -837,6 +838,11 @@ 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 = 1; + } + for (i = 0; i < count; i++) { /* Do not add to override if the map failed. */ if (map_ops[i].status) @@ -855,6 +861,9 @@ 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); @@ -862,7 +871,7 @@ EXPORT_SYMBOL_GPL(gnttab_map_refs); int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops, struct page **pages, unsigned int count, bool clear_pte) { - int i, ret; + int i, ret, lazy = 0; ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count); if (ret) @@ -871,12 +880,20 @@ 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 = 1; + } + 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);