From 11fcbe5a4688e4217ecbd8bd19ee23a4e5c1d709 Mon Sep 17 00:00:00 2001
From: Stephen Gregoratto <dev@sgregoratto.me>
Date: Thu, 28 Sep 2023 18:19:38 +1000
Subject: [PATCH 1/3] gen_linux_syscalls: use default max output bytes

Apparently, 20KiB is not enough anymore.
---
 tools/generate_linux_syscalls.zig | 2 --
 1 file changed, 2 deletions(-)

diff --git a/tools/generate_linux_syscalls.zig b/tools/generate_linux_syscalls.zig
index 32e287b434..92fc2ac1df 100644
--- a/tools/generate_linux_syscalls.zig
+++ b/tools/generate_linux_syscalls.zig
@@ -262,7 +262,6 @@ pub fn main() !void {
             .argv = &child_args,
             .cwd = linux_path,
             .cwd_dir = linux_dir,
-            .max_output_bytes = 20 * 1024,
         });
         if (child_result.stderr.len > 0) std.debug.print("{s}\n", .{child_result.stderr});
 
@@ -324,7 +323,6 @@ pub fn main() !void {
             .argv = &child_args,
             .cwd = linux_path,
             .cwd_dir = linux_dir,
-            .max_output_bytes = 20 * 1024,
         });
         if (child_result.stderr.len > 0) std.debug.print("{s}\n", .{child_result.stderr});
 

From 5f456b2b97bc4a4c4860fd7cb6287c400e215eae Mon Sep 17 00:00:00 2001
From: Stephen Gregoratto <dev@sgregoratto.me>
Date: Thu, 28 Sep 2023 18:21:32 +1000
Subject: [PATCH 2/3] Update Linux syscalls for kernel 5.5

The latest addition is `cachestat`, which provides more detailed
information for paged files.
---
 lib/std/os/linux/syscalls.zig | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/std/os/linux/syscalls.zig b/lib/std/os/linux/syscalls.zig
index f176a434b4..b919c354c2 100644
--- a/lib/std/os/linux/syscalls.zig
+++ b/lib/std/os/linux/syscalls.zig
@@ -442,6 +442,7 @@ pub const X86 = enum(usize) {
     process_mrelease = 448,
     futex_waitv = 449,
     set_mempolicy_home_node = 450,
+    cachestat = 451,
 };
 
 pub const X64 = enum(usize) {
@@ -807,6 +808,7 @@ pub const X64 = enum(usize) {
     process_mrelease = 448,
     futex_waitv = 449,
     set_mempolicy_home_node = 450,
+    cachestat = 451,
 };
 
 pub const Arm = enum(usize) {
@@ -1215,6 +1217,7 @@ pub const Arm = enum(usize) {
     process_mrelease = 448,
     futex_waitv = 449,
     set_mempolicy_home_node = 450,
+    cachestat = 451,
 
     breakpoint = arm_base + 1,
     cacheflush = arm_base + 2,
@@ -1607,6 +1610,7 @@ pub const Sparc64 = enum(usize) {
     process_mrelease = 448,
     futex_waitv = 449,
     set_mempolicy_home_node = 450,
+    cachestat = 451,
 };
 
 pub const Mips = enum(usize) {
@@ -2030,6 +2034,7 @@ pub const Mips = enum(usize) {
     process_mrelease = Linux + 448,
     futex_waitv = Linux + 449,
     set_mempolicy_home_node = Linux + 450,
+    cachestat = Linux + 451,
 };
 
 pub const Mips64 = enum(usize) {
@@ -2389,6 +2394,7 @@ pub const Mips64 = enum(usize) {
     process_mrelease = Linux + 448,
     futex_waitv = Linux + 449,
     set_mempolicy_home_node = Linux + 450,
+    cachestat = Linux + 451,
 };
 
 pub const PowerPC = enum(usize) {
@@ -2823,6 +2829,7 @@ pub const PowerPC = enum(usize) {
     process_mrelease = 448,
     futex_waitv = 449,
     set_mempolicy_home_node = 450,
+    cachestat = 451,
 };
 
 pub const PowerPC64 = enum(usize) {
@@ -3229,6 +3236,7 @@ pub const PowerPC64 = enum(usize) {
     process_mrelease = 448,
     futex_waitv = 449,
     set_mempolicy_home_node = 450,
+    cachestat = 451,
 };
 
 pub const Arm64 = enum(usize) {
@@ -3538,6 +3546,7 @@ pub const Arm64 = enum(usize) {
     process_mrelease = 448,
     futex_waitv = 449,
     set_mempolicy_home_node = 450,
+    cachestat = 451,
 };
 
 pub const RiscV64 = enum(usize) {
@@ -3848,6 +3857,7 @@ pub const RiscV64 = enum(usize) {
     process_mrelease = 448,
     futex_waitv = 449,
     set_mempolicy_home_node = 450,
+    cachestat = 451,
 
     riscv_flush_icache = arch_specific_syscall + 15,
 };

From bc0bf4e97ac7ac45731b7a7e629e680e51d8eefe Mon Sep 17 00:00:00 2001
From: Stephen Gregoratto <dev@sgregoratto.me>
Date: Thu, 28 Sep 2023 18:27:37 +1000
Subject: [PATCH 3/3] Linux: Add cachestat wrapper.

Can be tested using this program I whipped up:
https://gist.github.com/The-King-of-Toasters/aee448f5975c50f735fd1946794574f7
---
 lib/std/os/linux.zig | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index 4a59446a8d..dea3cea875 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -1876,6 +1876,21 @@ pub fn ptrace(
     );
 }
 
+pub fn cachestat(
+    fd: fd_t,
+    cstat_range: *const cache_stat_range,
+    cstat: *cache_stat,
+    flags: u32,
+) usize {
+    return syscall4(
+        .cachestat,
+        @as(usize, @bitCast(@as(isize, fd))),
+        @intFromPtr(cstat_range),
+        @intFromPtr(cstat),
+        flags,
+    );
+}
+
 pub const E = switch (native_arch) {
     .mips, .mipsel => @import("linux/errno/mips.zig").E,
     .sparc, .sparcel, .sparc64 => @import("linux/errno/sparc.zig").E,
@@ -5829,3 +5844,16 @@ pub const PTRACE = struct {
     pub const SECCOMP_GET_METADATA = 0x420d;
     pub const GET_SYSCALL_INFO = 0x420e;
 };
+
+pub const cache_stat_range = extern struct {
+    off: u64,
+    len: u64,
+};
+
+pub const cache_stat = extern struct {
+    cache: u64,
+    dirty: u64,
+    writeback: u64,
+    evicted: u64,
+    recently_evicted: u64,
+};