On 2023/7/24 23:21, James Clark wrote: > > > On 11/07/2023 02:41, 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 >> maintain 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 -EINVAL 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 22 (Invalid argument) >> > > Hi Shuai, Hi, James, > > Now that I think about this, isn't the previous error "failed to mmap > with 12 (Cannot allocate memory)" better than "failed to mmap with 22 > (Invalid argument)"? If I see a "invalid argument", I am expected to check my perf command first. But for "Cannot allocate memory", I will doubt that the system have problem but I dont have any idea about. IMO, I prefer "invalid argument". But I can change back to previous error message if you insist. > And you might want to split the doc change out if they are going to be > merged through separate trees. Will do that. > > And one comment below: > >> Signed-off-by: Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx> >> --- >> changes since v2: >> - remove unnecessary overflow check (per Peter) >> >> changes since v1: >> - drop out patch2 because it has been fixed on upstream (Thanks James for reminding) >> - move sanity check into rb_alloc_aux (per Leo) >> - add overflow check (per James) >> --- >> kernel/events/ring_buffer.c | 3 +++ >> tools/perf/Documentation/perf-record.txt | 3 ++- >> 2 files changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c >> index a0433f37b024..5933ce45c68a 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 */ >> + if (get_order((unsigned long)nr_pages * sizeof(void *)) > MAX_ORDER) >> + return -EINVAL; >> rb->aux_pages = kcalloc_node(nr_pages, sizeof(void *), GFP_KERNEL, >> node); >> if (!rb->aux_pages) >> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt >> index 680396c56bd1..5d8d3ad084ed 100644 >> --- a/tools/perf/Documentation/perf-record.txt >> +++ b/tools/perf/Documentation/perf-record.txt >> @@ -290,7 +290,8 @@ OPTIONS >> specification with appended unit character - B/K/M/G. The >> size is rounded up to have nearest pages power of two value. >> Also, by adding a comma, the number of mmap pages for AUX >> - area tracing can be specified. >> + area tracing can be specified. With MAX_ORDER set as 10 on >> + arm64 platform , the maximum AUX area is limited to 2GiB. > > Minor nit: I wouldn't expect a Perf tool user to know what "MAX_ORDER" > is, and I don't think the limitation is Arm specific? Maybe something in > more relevant terms is more useful: > > The maximum AUX area is limited by the page size of the system. For > example with 4K pages configured, the maximum is 2GiB. Agreed. Will change it. > > Thanks > James Thank you for valuable comments. Best Regards, Shuai > >> >> -g:: >> Enables call-graph (stack chain/backtrace) recording for both
