linux-kernel - Re: [RFC PATCH v3 30/37] perf bpf: Add bpf-loader and open ELF object files

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Date:	Mon, 25 May 2015 19:47:01 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Jiri Olsa <jolsa@...hat.com>
CC:	<paulus@...ba.org>, <a.p.zijlstra@...llo.nl>, <mingo@...hat.com>,
	<acme@...nel.org>, <namhyung@...nel.org>, <jolsa@...nel.org>,
	<dsahern@...il.com>, <ast@...mgrid.com>, <daniel@...earbox.net>,
	<brendan.d.gregg@...il.com>, <masami.hiramatsu.pt@...achi.com>,
	<lizefan@...wei.com>, <linux-kernel@...r.kernel.org>,
	<pi3orama@....com>
Subject: Re: [RFC PATCH v3 30/37] perf bpf: Add bpf-loader and open ELF object
 files



On 2015/5/23 1:24, Jiri Olsa wrote:
> On Sun, May 17, 2015 at 10:56:55AM +0000, Wang Nan wrote:
>
> SNIP
>
>> +#define DEFINE_PRINT_FN(name, level) \
>> +static int libbpf_##name(const char *fmt, ...)	\
>> +{						\
>> +	va_list args;				\
>> +	int ret;				\
>> +						\
>> +	va_start(args, fmt);			\
>> +	ret = veprintf(level, verbose, pr_fmt(fmt), args);\
>> +	va_end(args);				\
>> +	return ret;				\
>> +}
>> +
>> +DEFINE_PRINT_FN(warning, 0)
>> +DEFINE_PRINT_FN(info, 0)
>> +DEFINE_PRINT_FN(debug, 1)
>> +
>> +static bool libbpf_inited = false;
>> +
>> +#define MAX_OBJECTS	128
>> +
>> +struct {
>> +	struct bpf_object *objects[MAX_OBJECTS];
>> +	size_t nr_objects;
>> +} params;
> apart from that we dont like this kind of static stuff, this seems like
> nice case for having simple handler like 'struct bpf_objects' carrying
> the above data.. what do I miss?

I want to avoid fragmented memory allocation for storing bpf_object 
pointers.
Storing them together into an array can make code simpler. I think I can 
made
something like 'struct bpf_object *bpf_next_object(obj)' in libbpf so we can
iterate over each loaded bpf objects, then this array and nr_objects can be
hidden.

> also params should actually be static right?
>
> jirka


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