[PATCH bpf-next] bpf: Cache the last valid build_id.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



For binaries that are statically linked, consecutive stack frames are
likely to be in the same VMA and therefore have the same build id.
As an optimization for this case, we can cache the previous frame's
VMA, if the new frame has the same VMA as the previous one, reuse the
previous one's build id. We are holding the MM locks as reader across
the entire loop, so we don't need to worry about VMA going away.

Tested through "stacktrace_build_id" and "stacktrace_build_id_nmi" in
test_progs.

Suggested-by: Greg Thelen <gthelen@xxxxxxxxxx>
Signed-off-by: Hao Luo <haoluo@xxxxxxxxxx>
---
 kernel/bpf/stackmap.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 22c8ae94e4c1..280b9198af27 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -132,7 +132,8 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 	int i;
 	struct mmap_unlock_irq_work *work = NULL;
 	bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
-	struct vm_area_struct *vma;
+	struct vm_area_struct *vma, *prev_vma = NULL;
+	const char *prev_build_id;
 
 	/* If the irq_work is in use, fall back to report ips. Same
 	 * fallback is used for kernel stack (!user) on a stackmap with
@@ -151,6 +152,11 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 
 	for (i = 0; i < trace_nr; i++) {
 		vma = find_vma(current->mm, ips[i]);
+		if (vma && vma == prev_vma) {
+			memcpy(id_offs[i].build_id, prev_build_id,
+			       BUILD_ID_SIZE_MAX);
+			goto build_id_valid;
+		}
 		if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {
 			/* per entry fall back to ips */
 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
@@ -158,9 +164,12 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
 			continue;
 		}
+build_id_valid:
 		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
 			- vma->vm_start;
 		id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
+		prev_vma = vma;
+		prev_build_id = id_offs[i].build_id;
 	}
 	bpf_mmap_unlock_mm(work, current->mm);
 }
-- 
2.35.1.473.g83b2b277ed-goog




[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux