tools/readahead: Migrate to kfunc/kretfunc
# When copying or porting, include this comment.
#
# 20-Aug-2020 Suchakra Sharma Ported from bpftrace to BCC
+# 17-Sep-2021 Hengqi Chen Migrated to kfunc
from __future__ import print_function
from bcc import BPF
@@ -34,7 +35,7 @@ if not args.duration:
args.duration = 99999999
# BPF program
-program = """
+bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/mm_types.h>
@@ -42,7 +43,9 @@ BPF_HASH(flag, u32, u8); // used to track if we are in do_page_cache_
BPF_HASH(birth, struct page*, u64); // used to track timestamps of cache alloc'ed page
BPF_ARRAY(pages); // increment/decrement readahead pages
BPF_HISTOGRAM(dist);
+"""
+bpf_text_kprobe = """
int entry__do_page_cache_readahead(struct pt_regs *ctx) {
u32 pid;
u8 one = 1;
@@ -89,7 +92,66 @@ int entry_mark_page_accessed(struct pt_regs *ctx) {
}
"""
-b = BPF(text=program)
+bpf_text_kfunc = """
+KFUNC_PROBE(RA_FUNC, void *unused)
+{
+ u32 pid = bpf_get_current_pid_tgid();
+ u8 one = 1;
+
+ flag.update(&pid, &one);
+ return 0;
+}
+
+KRETFUNC_PROBE(RA_FUNC, void *unused)
+{
+ u32 pid = bpf_get_current_pid_tgid();
+ u8 zero = 0;
+
+ flag.update(&pid, &zero);
+ return 0;
+}
+
+KRETFUNC_PROBE(__page_cache_alloc, gfp_t gfp, struct page *retval)
+{
+ u64 ts;
+ u32 zero = 0; // static key for accessing pages[0]
+ u32 pid = bpf_get_current_pid_tgid();
+ u8 *f = flag.lookup(&pid);
+
+ if (f != NULL && *f == 1) {
+ ts = bpf_ktime_get_ns();
+ birth.update(&retval, &ts);
+ pages.atomic_increment(zero);
+ }
+ return 0;
+}
+
+KFUNC_PROBE(mark_page_accessed, struct page *arg0)
+{
+ u64 ts, delta;
+ u32 zero = 0; // static key for accessing pages[0]
+ u64 *bts = birth.lookup(&arg0);
+
+ if (bts != NULL) {
+ delta = bpf_ktime_get_ns() - *bts;
+ dist.atomic_increment(bpf_log2l(delta/1000000));
+ pages.atomic_increment(zero, -1);
+ birth.delete(&arg0); // remove the entry from hashmap
+ }
+ return 0;
+}
+"""
+
+if BPF.support_kfunc():
+ if BPF.get_kprobe_functions(b"__do_page_cache_readahead"):
+ ra_func = "__do_page_cache_readahead"
+ else:
+ ra_func = "do_page_cache_ra"
+ bpf_text += bpf_text_kfunc.replace("RA_FUNC", ra_func)
+ b = BPF(text=bpf_text)
+else:
+ bpf_text += bpf_text_kprobe
+ b = BPF(text=bpf_text)
if BPF.get_kprobe_functions(b"__do_page_cache_readahead"):
ra_event = "__do_page_cache_readahead"
else:
