On 9/22/2018 10:07 PM, Sai Prakash Ranjan wrote:
On 9/22/2018 2:35 PM, Joel Fernandes wrote:
On Sat, Sep 8, 2018 at 4:28 PM Sai Prakash Ranjan
<saiprakash.ranjan@xxxxxxxxxxxxxx> wrote:
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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