tools/readahead: Migrate to kfunc/kretfunc

Signed-off-by: Hengqi Chen <[email protected]>

tools/readahead.py

@@ -10,7 +10,8 @@
 # published by Addison Wesley. ISBN-13: 9780136554820
 # When copying or porting, include this comment.
 #
-# 20-Aug-2020 Suchakra Sharma Ported from bpftrace to BCC
+# 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
@@ -34,15 +35,17 @@
  args.duration = 99999999
 
 # BPF program
-program = """
+bpf_text = """
 #include <uapi/linux/ptrace.h>
 #include <linux/mm_types.h>
 
 BPF_HASH(flag, u32, u8); // used to track if we are in do_page_cache_readahead()
 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;
@@ -89,15 +92,74 @@
 }
 """
 
-b = BPF(text=program)
-if BPF.get_kprobe_functions(b"__do_page_cache_readahead"):
- ra_event = "__do_page_cache_readahead"
+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:
- ra_event = "do_page_cache_ra"
-b.attach_kprobe(event=ra_event, fn_name="entry__do_page_cache_readahead")
-b.attach_kretprobe(event=ra_event, fn_name="exit__do_page_cache_readahead")
-b.attach_kretprobe(event="__page_cache_alloc", fn_name="exit__page_cache_alloc")
-b.attach_kprobe(event="mark_page_accessed", fn_name="entry_mark_page_accessed")
+ 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:
+ ra_event = "do_page_cache_ra"
+ b.attach_kprobe(event=ra_event, fn_name="entry__do_page_cache_readahead")
+ b.attach_kretprobe(event=ra_event, fn_name="exit__do_page_cache_readahead")
+ b.attach_kretprobe(event="__page_cache_alloc", fn_name="exit__page_cache_alloc")
+ b.attach_kprobe(event="mark_page_accessed", fn_name="entry_mark_page_accessed")
 
 # header
 print("Tracing... Hit Ctrl-C to end.")