On Fri, Sep 6, 2024 at 11:26 AM Ian Forbes <ian.forbes@xxxxxxxxxxxx> wrote:
>
> On Thu, Sep 5, 2024 at 10:59 PM Zack Rusin <zack.rusin@xxxxxxxxxxxx> wrote:
> >
> >
> > In general it looks good but what's the reason for the submit_time?
> >
> > z
>
> So you can get an approximate time of how long each command buffer takes.
> You can then use it to construct a histogram or look for outliers
> using bpftrace.
> Useful when doing performance analysis to determine if slowdowns are being
> caused by the host or the guest driver.
>
> $ sudo bpftrace -e 'tracepoint:vmwgfx:vmwgfx_cmdbuf_done{
> if(args->status == 1) { $elapsed =(jiffies -
> args->header->submit_time); @exec_times = hist($elapsed); } }'
> Attaching 1 probe...
Can't you do the same with just:
bpftrace -e 'kprobe:vmw_cmdbuf_header_submit { @start[tid] = nsecs; }
kretprobe:vmw_cmdbuf_header_submit /@start[tid]/ { @ns[comm] =
hist(nsecs - @start[tid]); delete(@start[tid]); }'
Or kfunc/kretfunc if you want to condition it based on args->status?
z
