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@@ -396,6 +396,13 @@ int __page_mapcount(struct page *page)
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}
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EXPORT_SYMBOL_GPL(__page_mapcount);
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+int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
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+int sysctl_overcommit_ratio __read_mostly = 50;
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+unsigned long sysctl_overcommit_kbytes __read_mostly;
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+int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
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+unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
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+unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
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+
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int overcommit_ratio_handler(struct ctl_table *table, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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@@ -437,6 +444,123 @@ unsigned long vm_commit_limit(void)
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return allowed;
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}
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+/*
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+ * Make sure vm_committed_as in one cacheline and not cacheline shared with
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+ * other variables. It can be updated by several CPUs frequently.
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+ */
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+struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
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+
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+/*
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+ * The global memory commitment made in the system can be a metric
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+ * that can be used to drive ballooning decisions when Linux is hosted
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+ * as a guest. On Hyper-V, the host implements a policy engine for dynamically
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+ * balancing memory across competing virtual machines that are hosted.
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+ * Several metrics drive this policy engine including the guest reported
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+ * memory commitment.
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+ */
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+unsigned long vm_memory_committed(void)
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+{
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+ return percpu_counter_read_positive(&vm_committed_as);
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+}
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+EXPORT_SYMBOL_GPL(vm_memory_committed);
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+
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+/*
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+ * Check that a process has enough memory to allocate a new virtual
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+ * mapping. 0 means there is enough memory for the allocation to
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+ * succeed and -ENOMEM implies there is not.
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+ *
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+ * We currently support three overcommit policies, which are set via the
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+ * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting
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+ *
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+ * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
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+ * Additional code 2002 Jul 20 by Robert Love.
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+ *
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+ * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
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+ *
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+ * Note this is a helper function intended to be used by LSMs which
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+ * wish to use this logic.
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+ */
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+int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
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+{
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+ long free, allowed, reserve;
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+
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+ VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
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+ -(s64)vm_committed_as_batch * num_online_cpus(),
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+ "memory commitment underflow");
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+
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+ vm_acct_memory(pages);
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+
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+ /*
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+ * Sometimes we want to use more memory than we have
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+ */
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+ if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
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+ return 0;
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+
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+ if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
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+ free = global_page_state(NR_FREE_PAGES);
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+ free += global_page_state(NR_FILE_PAGES);
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+
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+ /*
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+ * shmem pages shouldn't be counted as free in this
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+ * case, they can't be purged, only swapped out, and
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+ * that won't affect the overall amount of available
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+ * memory in the system.
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+ */
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+ free -= global_page_state(NR_SHMEM);
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+
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+ free += get_nr_swap_pages();
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+
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+ /*
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+ * Any slabs which are created with the
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+ * SLAB_RECLAIM_ACCOUNT flag claim to have contents
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+ * which are reclaimable, under pressure. The dentry
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+ * cache and most inode caches should fall into this
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+ */
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+ free += global_page_state(NR_SLAB_RECLAIMABLE);
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+
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+ /*
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+ * Leave reserved pages. The pages are not for anonymous pages.
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+ */
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+ if (free <= totalreserve_pages)
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+ goto error;
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+ else
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+ free -= totalreserve_pages;
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+
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+ /*
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+ * Reserve some for root
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+ */
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+ if (!cap_sys_admin)
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+ free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
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+
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+ if (free > pages)
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+ return 0;
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+
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+ goto error;
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+ }
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+
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+ allowed = vm_commit_limit();
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+ /*
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+ * Reserve some for root
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+ */
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+ if (!cap_sys_admin)
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+ allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
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+
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+ /*
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+ * Don't let a single process grow so big a user can't recover
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+ */
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+ if (mm) {
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+ reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
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+ allowed -= min_t(long, mm->total_vm / 32, reserve);
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+ }
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+
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+ if (percpu_counter_read_positive(&vm_committed_as) < allowed)
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+ return 0;
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+error:
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+ vm_unacct_memory(pages);
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+
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+ return -ENOMEM;
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+}
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+
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/**
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* get_cmdline() - copy the cmdline value to a buffer.
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* @task: the task whose cmdline value to copy.
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Andrey Ryabinin