/**
 * Why a limit did or did not accompany a usage reading.
 *
 *   available    A finite positive limit was read; `limitBytes` is set.
 *   unlimited    The cgroup reports no limit: v2 `max`, or v1's 2^63-1 sentinel
 *                (which gVisor sandboxes always report, because the real limit
 *                is enforced on the host cgroup outside the sandbox).
 *   unreadable   The limit file could not be read at all.
 *
 * The last two both omit `limitBytes`, so without this they are indistinguishable
 * to a consumer -- an unreadable limit is a genuine fault worth alerting on,
 * while an unlimited one is the normal steady state under gVisor.
 */
type CgroupLimitState = "available" | "unlimited" | "unreadable";
interface CgroupMemory {
    currentBytes: number;
    /** Set only when `limitState` is `available`. */
    limitBytes?: number;
    /** Absent whenever `limitBytes` is, since it is derived from it. */
    usageRatio?: number;
    /** Always set; see {@link CgroupLimitState}. */
    limitState: CgroupLimitState;
}
export interface MemoryMetricsOptions {
    /**
     * Cgroup filesystem root to read from. Defaults to the real `/sys/fs/cgroup`;
     * overridden only by tests, which point it at a fixture directory.
     */
    cgroupRoot?: string;
}
export declare function readCgroupMemory(root?: string): CgroupMemory | undefined;
export declare function startMemoryMetrics(options?: MemoryMetricsOptions): void;
export declare function stopMemoryMetrics(): void;
export {};
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