linux-kernel - Re: [PATCH v3 2/2] Support interactive annotation of code without symbols

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Date:   Mon, 24 Feb 2020 21:46:55 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Jin, Yao" <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v3 2/2] Support interactive annotation of code without
 symbols

On Mon, Feb 24, 2020 at 11:39:43PM +0800, Jin, Yao wrote:

SNIP

> > > +	sym = symbol__new(addr, ANNOTATION_DUMMY_LEN, 0, 0, name);
> > > +	if (sym) {
> > > +		src = symbol__hists(sym, 1);
> > > +		if (!src) {
> > > +			symbol__delete(sym);
> > > +			return NULL;
> > > +		}
> > 
> > hi,
> > I like the patchset:
> > 
> > Acked-by: Jiri Olsa <jolsa@...hat.com>
> > 
> > could you please also check if we can do this earlier,
> > so the dummy symbol is actualy collecting all the hits?
> > 
> > like within the symbol__inc_addr_samples function,
> > but I mght be missing something..
> > 
> > thanks,
> > jirka
> > 
> 
> Thanks so much for like and ack this patchset!
> 
> For your suggestion, I had thought about the similar idea before. Maybe we
> can, but we need to process some cases.
> 
> Say the first address is 0x1000 and the dummy symbol size is 256. We create
> a new dummy symbol for this address (start address is 0x1000 and end address
> is 0x1100).
> 
> If the second address is 0x1010, we can't create a new dummy symbol for this
> address directly. On the contrary, we need to search the dummy symbol list
> by the address first. If the dummy symbol is found then reuse this symbol.
> 
> This idea is a bit more complicated than current patchset in implementation
> but it can collect the hits for the dummy symbols, that's the advantage. The
> advantage of current patchset is it's very simple. :)

ah right, we dont know the symbol's size.. perhaps we could hold
histogram of unresolved addresses and use it later on when displaying
the annotation for the particular unresolved address.. but then
how to bucket the counts for accounting.. yep, it seems tricky ;-)

> 
> Accept current patchset or rewrite for the new idea, both OK for me. :)

I think you it can be build on top of this

thanks,
jirka