On Fri, Aug 04, 2023 at 03:29:44PM +0800, Shuai Xue wrote: > When perf-record with a large AUX area, e.g 4GB, it fails with: > > #perf record -C 0 -m ,4G -e arm_spe_0// -- sleep 1 > failed to mmap with 12 (Cannot allocate memory) > > and it reveals a WARNING with __alloc_pages(): > > [ 66.595604] ------------[ cut here ]------------ > [ 66.600206] WARNING: CPU: 44 PID: 17573 at mm/page_alloc.c:5568 __alloc_pages+0x1ec/0x248 > [ 66.608375] Modules linked in: ip6table_filter(E) ip6_tables(E) iptable_filter(E) ebtable_nat(E) ebtables(E) aes_ce_blk(E) vfat(E) fat(E) aes_ce_cipher(E) crct10dif_ce(E) ghash_ce(E) sm4_ce_cipher(E) sm4(E) sha2_ce(E) sha256_arm64(E) sha1_ce(E) acpi_ipmi(E) sbsa_gwdt(E) sg(E) ipmi_si(E) ipmi_devintf(E) ipmi_msghandler(E) ip_tables(E) sd_mod(E) ast(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) nvme(E) sysimgblt(E) i2c_algo_bit(E) nvme_core(E) drm_shmem_helper(E) ahci(E) t10_pi(E) libahci(E) drm(E) crc64_rocksoft(E) i40e(E) crc64(E) libata(E) i2c_core(E) > [ 66.657719] CPU: 44 PID: 17573 Comm: perf Kdump: loaded Tainted: G E 6.3.0-rc4+ #58 > [ 66.666749] Hardware name: Default Default/Default, BIOS 1.2.M1.AL.P.139.00 03/22/2023 > [ 66.674650] pstate: 23400009 (nzCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) > [ 66.681597] pc : __alloc_pages+0x1ec/0x248 > [ 66.685680] lr : __kmalloc_large_node+0xc0/0x1f8 > [ 66.690285] sp : ffff800020523980 > [ 66.693585] pmr_save: 000000e0 > [ 66.696624] x29: ffff800020523980 x28: ffff000832975800 x27: 0000000000000000 > [ 66.703746] x26: 0000000000100000 x25: 0000000000100000 x24: ffff8000083615d0 > [ 66.710866] x23: 0000000000040dc0 x22: ffff000823d6d140 x21: 000000000000000b > [ 66.717987] x20: 000000000000000b x19: 0000000000000000 x18: 0000000000000030 > [ 66.725108] x17: 0000000000000000 x16: ffff800008f05be8 x15: ffff000823d6d6d0 > [ 66.732229] x14: 0000000000000000 x13: 343373656761705f x12: 726e202c30206574 > [ 66.739350] x11: 00000000ffff7fff x10: 00000000ffff7fff x9 : ffff8000083af570 > [ 66.746471] x8 : 00000000000bffe8 x7 : c0000000ffff7fff x6 : 000000000005fff4 > [ 66.753592] x5 : 0000000000000000 x4 : ffff000823d6d8d8 x3 : 0000000000000000 > [ 66.760713] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 0000000000040dc0 > [ 66.767834] Call trace: > [ 66.770267] __alloc_pages+0x1ec/0x248 > [ 66.774003] __kmalloc_large_node+0xc0/0x1f8 > [ 66.778259] __kmalloc_node+0x134/0x1e8 > [ 66.782081] rb_alloc_aux+0xe0/0x298 > [ 66.785643] perf_mmap+0x440/0x660 > [ 66.789031] mmap_region+0x308/0x8a8 > [ 66.792593] do_mmap+0x3c0/0x528 > [ 66.795807] vm_mmap_pgoff+0xf4/0x1b8 > [ 66.799456] ksys_mmap_pgoff+0x18c/0x218 > [ 66.803365] __arm64_sys_mmap+0x38/0x58 > [ 66.807187] invoke_syscall+0x50/0x128 > [ 66.810922] el0_svc_common.constprop.0+0x58/0x188 > [ 66.815698] do_el0_svc+0x34/0x50 > [ 66.818999] el0_svc+0x34/0x108 > [ 66.822127] el0t_64_sync_handler+0xb8/0xc0 > [ 66.826296] el0t_64_sync+0x1a4/0x1a8 > [ 66.829946] ---[ end trace 0000000000000000 ]--- > > 'rb->aux_pages' allocated by kcalloc() is a pointer array which is used to > maintains AUX trace pages. The allocated page for this array is physically > contiguous (and virtually contiguous) with an order of 0..MAX_ORDER. If the > size of pointer array crosses the limitation set by MAX_ORDER, it reveals a > WARNING. > > So bail out early with -ENOMEM if the request AUX area is out of bound, > e.g.: > > #perf record -C 0 -m ,4G -e arm_spe_0// -- sleep 1 > failed to mmap with 12 (Cannot allocate memory) > > Signed-off-by: Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx> > --- > kernel/events/ring_buffer.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c > index a0433f37b024..c445e927368d 100644 > --- a/kernel/events/ring_buffer.c > +++ b/kernel/events/ring_buffer.c > @@ -699,6 +699,9 @@ int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event, > watermark = 0; > } > > + /* Can't allocate more than MAX_ORDER */ The comment is confused. I'd like to refine it as: /* * kcalloc_node() is unable to allocate buffer if the size is larger * than: PAGE_SIZE << MAX_ORDER; directly bail out in this case. */ To be honest, I am not sure if perf core maintainers like this kind thing or not. Please seek their opinion before you move forward. Thanks, Leo > + if (get_order((unsigned long)nr_pages * sizeof(void *)) > MAX_ORDER) > + return -ENOMEM; > rb->aux_pages = kcalloc_node(nr_pages, sizeof(void *), GFP_KERNEL, > node); > if (!rb->aux_pages) > -- > 2.39.3 >
