On Fri Jul 17, 2026 at 7:37 AM EDT, Jiayuan Chen wrote: > Allocate and free arena pages, both from BPF and via user-space fault-in, > and check that the map's memlock in fdinfo tracks the number of pages that > are actually populated. > > Like the other arena tests it runs serially. > > test: > ./test_progs -a arena_mem_usage > #5 arena_mem_usage:OK > Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED > > Signed-off-by: Jiayuan Chen <[email protected]>
Reviewed-by: Emil Tsalapatis <[email protected]> The Sashiko nit is worth addressing, but overall looks fine. > --- > .../bpf/prog_tests/arena_mem_usage.c | 122 ++++++++++++++++++ > .../selftests/bpf/progs/arena_mem_usage.c | 40 ++++++ > 2 files changed, 162 insertions(+) > create mode 100644 tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c > create mode 100644 tools/testing/selftests/bpf/progs/arena_mem_usage.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c > b/tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c > new file mode 100644 > index 000000000000..14c2d1a1d673 > --- /dev/null > +++ b/tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c > @@ -0,0 +1,122 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#include <test_progs.h> > +#include <sys/user.h> > +#ifndef PAGE_SIZE /* on some archs it comes in sys/user.h */ > +#include <unistd.h> > +#define PAGE_SIZE getpagesize() > +#endif > + > +#include "arena_mem_usage.skel.h" > + > +/* > + * arena_map_mem_usage() is surfaced to user space through the map's > + * /proc/<pid>/fdinfo/<fd> "memlock:" line (the same value bpftool map show > + * prints). Read it directly so the test has no external dependency. > + */ > +static long map_memlock(int map_fd) > +{ > + char path[64], line[128]; > + long memlock = -1; > + FILE *f; > + > + snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", map_fd); > + f = fopen(path, "r"); > + if (!ASSERT_OK_PTR(f, "open_fdinfo")) > + return -1; > + while (fgets(line, sizeof(line), f)) { > + if (sscanf(line, "memlock:\t%ld", &memlock) == 1) > + break; > + } > + fclose(f); > + ASSERT_NEQ(memlock, -1, "parse_memlock"); > + return memlock; > +} > + > +static int run(struct bpf_program *prog, const char *name) > +{ > + LIBBPF_OPTS(bpf_test_run_opts, opts); > + int err = bpf_prog_test_run_opts(bpf_program__fd(prog), &opts); > + > + if (!ASSERT_OK(err, name)) > + return -1; > + if (!ASSERT_OK(opts.retval, name)) > + return -1; > + return 0; > +} > + > +void serial_test_arena_mem_usage(void) > +{ > + struct arena_mem_usage *skel; > + const long ps = PAGE_SIZE; > + char *base; > + size_t sz; > + int fd, i; > + > + skel = arena_mem_usage__open_and_load(); > + if (!ASSERT_OK_PTR(skel, "open_load")) > + return; > + fd = bpf_map__fd(skel->maps.arena); > + > + /* Fresh arena: no data pages, and the scratch page is not counted. */ > + ASSERT_EQ(map_memlock(fd), 0, "initial"); > + > + /* BPF-side allocation of 17 pages. */ > + skel->bss->alloc_cnt = 17; > + if (run(skel->progs.alloc, "alloc")) > + goto out; > + /* > + * A NULL ptr means bpf_arena_alloc_pages() itself failed (e.g. the host > + * is under memory pressure), not a miscount -- flag it distinctly so a > + * red CI run is not mistaken for a counting bug. > + */ > + if (!ASSERT_OK_PTR(skel->bss->ptr, "arena_alloc_pages")) > + goto out; > + ASSERT_EQ(map_memlock(fd), 17 * ps, "after_alloc"); > + > + /* Free a single page (arena_free_pages page_cnt==1 path). */ > + skel->bss->free_byte_off = 0; > + skel->bss->free_cnt = 1; > + if (run(skel->progs.free_pages, "free_one")) > + goto out; > + ASSERT_EQ(map_memlock(fd), 16 * ps, "after_free_one"); > + > + /* Free ten pages in one call (bulk path); only the freed pages count. > */ > + skel->bss->free_byte_off = 1 * ps; > + skel->bss->free_cnt = 10; > + if (run(skel->progs.free_pages, "free_bulk")) > + goto out; > + ASSERT_EQ(map_memlock(fd), 6 * ps, "after_free_bulk"); > + > + /* Free the remaining six -> arena empty again. */ > + skel->bss->free_byte_off = 11 * ps; > + skel->bss->free_cnt = 6; > + if (run(skel->progs.free_pages, "free_rest")) > + goto out; > + ASSERT_EQ(map_memlock(fd), 0, "after_free_rest"); > + > + /* > + * User-space fault-in: touching unallocated arena pages allocates them > + * through arena_vm_fault(). libbpf mmap()s the arena at map_extra > during > + * load, so bpf_map__initial_value() hands back that base. > + */ > + base = bpf_map__initial_value(skel->maps.arena, &sz); > + if (!ASSERT_OK_PTR(base, "arena_base")) > + goto out; > + for (i = 0; i < 8; i++) > + base[i * ps] = 1; > + ASSERT_EQ(map_memlock(fd), 8 * ps, "after_faultin"); > + > + /* > + * Free the faulted-in pages from BPF. They are mapped into the user vma > + * (elevated refcount), so this also exercises the zap path. > + */ > + skel->bss->ptr = base; > + skel->bss->free_byte_off = 0; > + skel->bss->free_cnt = 8; > + if (run(skel->progs.free_pages, "free_faulted")) > + goto out; > + ASSERT_EQ(map_memlock(fd), 0, "after_free_faulted"); > +out: > + arena_mem_usage__destroy(skel); > +} > diff --git a/tools/testing/selftests/bpf/progs/arena_mem_usage.c > b/tools/testing/selftests/bpf/progs/arena_mem_usage.c > new file mode 100644 > index 000000000000..455ecd669a5a > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/arena_mem_usage.c > @@ -0,0 +1,40 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#include <vmlinux.h> > +#include <bpf/bpf_helpers.h> > +#include "bpf_arena_common.h" > + > +struct { > + __uint(type, BPF_MAP_TYPE_ARENA); > + __uint(map_flags, BPF_F_MMAPABLE); > + __uint(max_entries, 1000); /* number of pages */ > +#ifdef __TARGET_ARCH_arm64 > + __ulong(map_extra, 0x1ull << 32); /* start of mmap() region */ > +#else > + __ulong(map_extra, 0x1ull << 44); /* start of mmap() region */ > +#endif > +} arena SEC(".maps"); > + > +void __arena *ptr; > +int alloc_cnt; /* in: pages to allocate */ > +long free_byte_off; /* in: byte offset within ptr to start freeing */ > +int free_cnt; /* in: pages to free */ > + > +SEC("syscall") > +int alloc(void *ctx) > +{ > + ptr = bpf_arena_alloc_pages(&arena, NULL, alloc_cnt, NUMA_NO_NODE, 0); > + /* Success/failure is checked from user space via skel->bss->ptr. */ > + return 0; > +} > + > +SEC("syscall") > +int free_pages(void *ctx) > +{ > + if (!ptr) > + return 1; > + bpf_arena_free_pages(&arena, (char __arena *)ptr + free_byte_off, > free_cnt); > + return 0; > +} > + > +char _license[] SEC("license") = "GPL";
