Hi experts,
Could anyone tell me whether Linux nvdimm driver is RT compatible?
When I was testing PMEM performance with fio using the following command, I got
calltrace below.
# fio -filename=/dev/pmem0s -direct=1 -iodepth 1 -thread -rw=randrw
-rwmixread=70 -ioengine=psync -bs=16k -size=1G -numjobs=30 -runtime=100
-group_reporting -name=mytest
BUG: scheduling while atomic: fio/2514/0x00000002
Modules linked in: intel_rapl nd_pmem nd_btt skx_edac iTCO_wdt
iTCO_vendor_support intel_powerclamp coretemp
crct10dif_pclmul crct10dif_common aesni_intel aes_x86_64 crypto_simd
cryptd i40e nvme glue_helper nvme_core lpc_ich i2c_i801 nfit pcc_cpufreq wmi
libnvdimm acpi_pad
acpi_power_meter
Preemption disabled at:
[<ffffffffc03608d9>] nd_region_acquire_lane+0x19/0x80 [libnvdimm]
CPU: 44 PID: 2514 Comm: fio Tainted: G W
4.18.20-rt8-preempt-rt #1
Call Trace:
dump_stack+0x4f/0x6a
? nd_region_acquire_lane+0x19/0x80 [libnvdimm]
__schedule_bug.cold.17+0x38/0x55
__schedule+0x484/0x6c0
? _raw_spin_lock+0x17/0x40
schedule+0x3d/0xe0
rt_spin_lock_slowlock_locked+0x118/0x2a0
rt_spin_lock_slowlock+0x57/0x90
rt_spin_lock+0x52/0x60
btt_write_pg.isra.16+0x280/0x4b0 [nd_btt]
btt_make_request+0x1b1/0x320 [nd_btt]
generic_make_request+0x1dc/0x3f0
submit_bio+0x49/0x140
nd_region_acquire_lane() disables preemption with get_cpu() which causes
"scheduling while atomic" spews on RT.
Is it safe to replace get_cpu()/put_cpu() with get_cpu_light()/put_cpu_light()
in nd_region_acquire_lane()/nd_region_release_lane()?
After this replacement, the codes protected by
nd_region_release_lane/nd_region_release_lane would become pre-emptible.
So are these codes reentrant?
Thanks,
Yongxin
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