Re: [PATCH 2/2] perf/ring_buffer: Fix high-order allocations for AUX space with correct MAX_ORDER limit

From: Shuai Xue
Date: Mon Jun 12 2023 - 04:36:17 EST



On 2023/6/12 16:30, Leo Yan wrote:
> On Mon, Jun 12, 2023 at 01:24:52PM +0800, Shuai Xue wrote:
>> When perf-record with a large AUX area, e.g 2GB:
>>
>> #perf record -C 0 -m ,2G -e arm_spe_0// -- sleep 1
>>
>> it reveals a WARNING with __alloc_pages:
>>
>> [ 48.888553] ------------[ cut here ]------------
>> [ 48.888559] WARNING: CPU: 39 PID: 17438 at mm/page_alloc.c:5568 __alloc_pages+0x1ec/0x248
>> [ 48.888569] Modules linked in: ip6table_filter(E) ip6_tables(E) iptable_filter(E) ebtable_nat(E) ebtables(E) vfat(E) fat(E) aes_ce_blk(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)
>> [ 48.888610] CPU: 39 PID: 17438 Comm: perf Kdump: loaded Tainted: G E 6.3.0-rc4+ #56
>> [ 48.888613] Hardware name: Default Default/Default, BIOS 1.2.M1.AL.P.139.00 03/22/2023
>> [ 48.888614] pstate: 23400009 (nzCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
>> [ 48.888616] pc : __alloc_pages+0x1ec/0x248
>> [ 48.888619] lr : rb_alloc_aux_page+0x78/0xe0
>> [ 48.888622] sp : ffff800037c5b9e0
>> [ 48.888623] pmr_save: 000000e0
>> [ 48.888624] x29: ffff800037c5b9e0 x28: ffff00082743b800 x27: 0000000000000000
>> [ 48.888627] x26: 0000000000080000 x25: ffff000000000000 x24: ffff000860b21380
>> [ 48.888629] x23: ffff8000093fd3c0 x22: ffff00081a4a2080 x21: 000000000000000b
>> [ 48.888631] x20: 0000000000000000 x19: 000000000000000b x18: 0000000000000020
>> [ 48.888634] x17: 0000000000000000 x16: ffff800008f05be8 x15: ffff00081a4a2610
>> [ 48.888636] x14: 0000000000000000 x13: 323173656761705f x12: ffff00477fffeb90
>> [ 48.888638] x11: 0000000000000000 x10: 0000000000000000 x9 : ffff8000083608a0
>> [ 48.888641] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000040
>> [ 48.888643] x5 : 000000000007f400 x4 : 0000000000000000 x3 : 0000000000000000
>> [ 48.888645] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 0000000000012dc0
>> [ 48.888648] Call trace:
>> [ 48.888650] __alloc_pages+0x1ec/0x248
>> [ 48.888653] rb_alloc_aux_page+0x78/0xe0
>> [ 48.888654] rb_alloc_aux+0x13c/0x298
>> [ 48.888656] perf_mmap+0x468/0x688
>> [ 48.888659] mmap_region+0x308/0x8a8
>> [ 48.888662] do_mmap+0x3c0/0x528
>> [ 48.888664] vm_mmap_pgoff+0xf4/0x1b8
>> [ 48.888666] ksys_mmap_pgoff+0x18c/0x218
>> [ 48.888668] __arm64_sys_mmap+0x38/0x58
>> [ 48.888671] invoke_syscall+0x50/0x128
>> [ 48.888673] el0_svc_common.constprop.0+0x58/0x188
>> [ 48.888674] do_el0_svc+0x34/0x50
>> [ 48.888676] el0_svc+0x34/0x108
>> [ 48.888679] el0t_64_sync_handler+0xb8/0xc0
>> [ 48.888681] el0t_64_sync+0x1a4/0x1a8
>> [ 48.888686] ---[ end trace 0000000000000000 ]---
>>
>> The problem is that the high-order pages for AUX area is allocated with
>> an order of MAX_ORDER. Obviously, this is a bogus.
>>
>> Fix it with an order of MAX_ORDER - 1 at maximum.
>>
>> Fixes: 0a4e38e64f5e ("perf: Support high-order allocations for AUX space")
>> Signed-off-by: Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx>
>
> LGTM:
>
> Reviewed-by: Leo Yan <leo.yan@xxxxxxxxxx>

Thank you :)

Cheers
Shuai

>
>> ---
>> kernel/events/ring_buffer.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
>> index 273a0fe..d6bbdb7 100644
>> --- a/kernel/events/ring_buffer.c
>> +++ b/kernel/events/ring_buffer.c
>> @@ -609,8 +609,8 @@ static struct page *rb_alloc_aux_page(int node, int order)
>> {
>> struct page *page;
>>
>> - if (order > MAX_ORDER)
>> - order = MAX_ORDER;
>> + if (order >= MAX_ORDER)
>> + order = MAX_ORDER - 1;
>>
>> do {
>> page = alloc_pages_node(node, PERF_AUX_GFP, order);
>> --
>> 1.8.3.1
>>