cachestat example

main.zig

const std = @import("std");
const os = std.os;
const process = std.process;
const linux = os.linux;

pub fn main() !void {
    var args = std.process.ArgIteratorPosix.init();
    _ = args.skip();
    const out = std.io.getStdOut();
    var buf = std.io.bufferedWriter(out.writer());
    const writer = buf.writer();

    const range = linux.cache_stat_range{
        .off = 0,
        .len = 0,
    };
    var stat: linux.cache_stat = undefined;
    while (args.next()) |arg| {
        const file = std.fs.cwd().openFile(arg, .{}) catch |err| switch (err) {
            error.AccessDenied, error.FileNotFound => continue,
            else => return err,
        };
        defer file.close();
        const meta = try file.metadata();
        if (meta.kind() != .file)
            continue;

        const rc = linux.cachestat(file.handle, &range, &stat, 0);
        if (rc != 0) {
            std.debug.print("could not get stat for file {s}, {}", .{ arg, rc });
            continue;
        }
        try writer.print(
            \\Page stats for {s}:
            \\Cached: {}
            \\Dirty: {}
            \\Marked for Writeback: {}
            \\Total Evicted: {}
            \\Recently Evicted: {}
            \\
            \\
        , .{
            arg,
            stat.cache,
            stat.dirty,
            stat.writeback,
            stat.evicted,
            stat.recently_evicted,
        });
    }

    try buf.flush();
}