On 9/22/2018 10:07 PM, Sai Prakash Ranjan wrote:

On 9/22/2018 2:35 PM, Joel Fernandes wrote:

quoted

On Sat, Sep 8, 2018 at 4:28 PM Sai Prakash Ranjan
[off-list ref] wrote:

quoted

Could you just split the pstore space into a per-cpu event buffer like
we are doing for ftrace-on-pstore? Then you don't need to lock. I fear
the lock contention will be apparent. The pstore code already has
plumbing to split the store buffer per CPU.

Hi Joel,

Thanks a lot for reviewing.

I just looked at per-cpu buffer for ftrace and itseems the pstore percpu 
records will need to be merged into one record if we add this support 
for events. Merging of ftrace logs is based on timestamp, but for events 
we do not have timestamp field (for this specific reason I have added 
timestamp field for IO event tracing so that atleast we can know the cpu 
number in pstore output). For example, the sched event pstore output 
below has no timestamp field, so how do we merge per-cpu logs?

# tail /sys/fs/pstore/event-ramoops-0
sched_waking: comm=rcu_sched pid=11 prio=120 target_cpu=002
sched_wakeup: comm=rcu_sched pid=11 prio=120 target_cpu=002

Also Pstore ftrace log format is fixed i.e.,(CPU:%d ts:%llu %08lx  %08lx 
  %pf <- %pF\n"), but different events will have different formats and 
we will not be able to add timestamp field like how pstore ftrace does 
using  pstore_ftrace_write_timestamp() and pstore_ftrace_read_timestamp().

Sorry if I am confusing you, I can explain better I guess.

To add to this on db410c board with the current patch I just measured 
average throughput of dd over 60 seconds with sched event tracing 
enabled (trace_event=sched tp_pstore) : 190 MB/s

# dd if=/dev/zero of=/dev/null status=progress
11402907648 bytes (11 GB, 11 GiB) copied, 60 s, 190 MB/s^C
22430312+0 records in
22430312+0 records out
11484319744 bytes (11 GB, 11 GiB) copied, 60.4277 s, 190 MB/s

It seems fine or maybe I am testing it wrongly? Anyways let me know if I 
can test any additional things in some different ways.

Thanks,
Sai

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