[lkml]   [2018]   [Sep]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 2/6] pstore: Add event tracing support
On 9/22/2018 2:35 PM, Joel Fernandes wrote:
> On Sat, Sep 8, 2018 at 4:28 PM Sai Prakash Ranjan
> <> 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.

> Also I think this spinlock can be moved further down.

OK. Something like this would suffice?

spin_lock_irqsave(&psinfo->buf_lock, flags);

record.buf = (char *)(seq->buffer);
record.size = seq->len;

spin_unlock_irqrestore(&psinfo->buf_lock, flags);

>> +
>> + trace_seq_init(&iter->seq);
>> + iter->ent = fbuffer->entry;
>> + event_call->event.funcs->trace(iter, 0, event);
>> + trace_seq_putc(&iter->seq, 0);
> Would it be possible to store the binary trace record in the pstore
> buffer instead of outputting text? I suspect that will both be faster
> and less space.

I will try this and come back.


QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

 \ /
  Last update: 2018-09-22 18:38    [W:0.130 / U:5.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site