From: Tamas K Lengyel <tamas.lengyel@intel.com>
To: xen-devel@lists.xenproject.org
Cc: "Tamas K Lengyel" <tamas@tklengyel.com>,
"Tamas K Lengyel" <tamas.lengyel@intel.com>,
"Wei Liu" <wl@xen.org>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"George Dunlap" <george.dunlap@eu.citrix.com>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"Ian Jackson" <ian.jackson@eu.citrix.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Julien Grall" <julien@xen.org>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: [Xen-devel] [PATCH v5 17/18] x86/mem_sharing: reset a fork
Date: Tue, 21 Jan 2020 09:49:50 -0800 [thread overview]
Message-ID: <3afdd6ef6a20236d62942df5958f046a8c3fae9c.1579628566.git.tamas.lengyel@intel.com> (raw)
In-Reply-To: <cover.1579628566.git.tamas.lengyel@intel.com>
Implement hypercall that allows a fork to shed all memory that got allocated
for it during its execution and re-load its vCPU context from the parent VM.
This allows the forked VM to reset into the same state the parent VM is in a
faster way then creating a new fork would be. Measurements show about a 2x
speedup during normal fuzzing operations. Performance may vary depending how
much memory got allocated for the forked VM. If it has been completely
deduplicated from the parent VM then creating a new fork would likely be more
performant.
Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
xen/arch/x86/mm/mem_sharing.c | 76 +++++++++++++++++++++++++++++++++++
xen/include/public/memory.h | 1 +
2 files changed, 77 insertions(+)
diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 749305417c..c185b0e7c4 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1611,6 +1611,59 @@ static int mem_sharing_fork(struct domain *d, struct domain *cd)
return rc;
}
+/*
+ * The fork reset operation is intended to be used on short-lived forks only.
+ * There is no hypercall continuation operation implemented for this reason.
+ * For forks that obtain a larger memory footprint it is likely going to be
+ * more performant to create a new fork instead of resetting an existing one.
+ *
+ * TODO: In case this hypercall would become useful on forks with larger memory
+ * footprints the hypercall continuation should be implemented.
+ */
+static int mem_sharing_fork_reset(struct domain *d, struct domain *cd)
+{
+ int rc;
+ struct p2m_domain* p2m = p2m_get_hostp2m(cd);
+ struct page_info *page, *tmp;
+
+ domain_pause(cd);
+
+ page_list_for_each_safe(page, tmp, &cd->page_list)
+ {
+ p2m_type_t p2mt;
+ p2m_access_t p2ma;
+ gfn_t gfn;
+ mfn_t mfn = page_to_mfn(page);
+
+ if ( !mfn_valid(mfn) )
+ continue;
+
+ gfn = mfn_to_gfn(cd, mfn);
+ mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &p2mt, &p2ma,
+ 0, NULL, false);
+
+ if ( !p2m_is_ram(p2mt) || p2m_is_shared(p2mt) )
+ continue;
+
+ /* take an extra reference */
+ if ( !get_page(page, cd) )
+ continue;
+
+ rc = p2m->set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_4K,
+ p2m_invalid, p2m_access_rwx, -1);
+ ASSERT(!rc);
+
+ put_page_alloc_ref(page);
+ put_page(page);
+ }
+
+ if ( !(rc = hvm_copy_context_and_params(d, cd)) )
+ fork_tsc(d, cd);
+
+ domain_unpause(cd);
+ return rc;
+}
+
int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
{
int rc;
@@ -1895,6 +1948,29 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
break;
}
+ case XENMEM_sharing_op_fork_reset:
+ {
+ struct domain *pd;
+
+ rc = -EINVAL;
+ if ( mso.u.fork._pad[0] || mso.u.fork._pad[1] ||
+ mso.u.fork._pad[2] )
+ goto out;
+
+ rc = -ENOSYS;
+ if ( !d->parent )
+ goto out;
+
+ rc = rcu_lock_live_remote_domain_by_id(d->parent->domain_id, &pd);
+ if ( rc )
+ goto out;
+
+ rc = mem_sharing_fork_reset(pd, d);
+
+ rcu_unlock_domain(pd);
+ break;
+ }
+
default:
rc = -ENOSYS;
break;
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index 90a3f4498e..e3d063e22e 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -483,6 +483,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_mem_access_op_t);
#define XENMEM_sharing_op_audit 7
#define XENMEM_sharing_op_range_share 8
#define XENMEM_sharing_op_fork 9
+#define XENMEM_sharing_op_fork_reset 10
#define XENMEM_SHARING_OP_S_HANDLE_INVALID (-10)
#define XENMEM_SHARING_OP_C_HANDLE_INVALID (-9)
--
2.20.1
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next prev parent reply other threads:[~2020-01-21 17:51 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-21 17:49 [Xen-devel] [PATCH v5 00/18] VM forking Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 01/18] x86/hvm: introduce hvm_copy_context_and_params Tamas K Lengyel
2020-01-22 15:00 ` Jan Beulich
2020-01-22 16:42 ` Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 02/18] xen/x86: Make hap_get_allocation accessible Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 03/18] x86/p2m: Allow p2m_get_page_from_gfn to return shared entries Tamas K Lengyel
2020-01-22 15:23 ` Jan Beulich
2020-01-22 16:51 ` Tamas K Lengyel
2020-01-22 16:55 ` Jan Beulich
2020-01-23 15:32 ` George Dunlap
2020-01-23 15:48 ` Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 04/18] x86/mem_sharing: make get_two_gfns take locks conditionally Tamas K Lengyel
2020-01-23 15:50 ` George Dunlap
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 05/18] x86/mem_sharing: drop flags from mem_sharing_unshare_page Tamas K Lengyel
2020-01-23 15:53 ` George Dunlap
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 06/18] x86/mem_sharing: don't try to unshare twice during page fault Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 07/18] x86/mem_sharing: define mem_sharing_domain to hold some scattered variables Tamas K Lengyel
2020-01-23 15:59 ` George Dunlap
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 08/18] x86/mem_sharing: Use INVALID_MFN and p2m_is_shared in relinquish_shared_pages Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 09/18] x86/mem_sharing: Make add_to_physmap static and shorten name Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 10/18] x86/mem_sharing: Convert MEM_SHARING_DESTROY_GFN to a bool Tamas K Lengyel
2020-01-23 16:14 ` George Dunlap
2020-01-23 16:23 ` Tamas K Lengyel
2020-01-23 16:32 ` George Dunlap
2020-01-23 16:37 ` Jan Beulich
2020-01-23 16:42 ` George Dunlap
2020-01-23 16:55 ` Jan Beulich
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 11/18] x86/mem_sharing: Replace MEM_SHARING_DEBUG with gdprintk Tamas K Lengyel
2020-01-22 15:30 ` Jan Beulich
2020-01-22 16:55 ` Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 12/18] x86/mem_sharing: Enable mem_sharing on first memop Tamas K Lengyel
2020-01-22 15:32 ` Jan Beulich
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 13/18] x86/mem_sharing: Skip xen heap pages in memshr nominate Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 14/18] x86/mem_sharing: use default_access in add_to_physmap Tamas K Lengyel
2020-01-22 15:35 ` Jan Beulich
2020-01-22 17:08 ` Tamas K Lengyel
2020-01-23 16:44 ` George Dunlap
2020-01-23 17:19 ` Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 15/18] xen/mem_sharing: VM forking Tamas K Lengyel
2020-01-23 17:21 ` George Dunlap
2020-01-23 17:30 ` Tamas K Lengyel
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 16/18] xen/mem_access: Use __get_gfn_type_access in set_mem_access Tamas K Lengyel
2020-01-21 17:49 ` Tamas K Lengyel [this message]
2020-01-21 17:49 ` [Xen-devel] [PATCH v5 18/18] xen/tools: VM forking toolstack side Tamas K Lengyel
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