On 2023/7/25 17:56, James Clark wrote: > > > On 25/07/2023 08:31, Shuai Xue wrote: >> >> >> 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. >> >> > > Maybe, but if a tool is currently doing something like an increasing > loop to check for the max possible aux buffer size and checking for "12 > (Cannot allocate memory)" then you could consider this change a > userspace breaking one. > > The script would probably just be checking for any error, but you never > know. > > I agree the error codes are quite non specific and don't really help > with showing the cause of the problem. But I can't see how the memory > one isn't more specific to the aux buffer size in this case. > > I searched for other errors returned after checking get_order() and I > found both -EINVAL and -ENOMEM, so if there is no consensus maybe it's > best to stick to the existing return value. Ok, I will change back to previous -ENOMEM :) Thank you. Best Regards, Shuai > > James > >>> 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
