linux-kernel - Re: [RFC][PATCH 1/2] perf: Add 'perf kmem' tool

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Date:	Fri, 20 Nov 2009 16:20:57 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [RFC][PATCH 1/2] perf: Add 'perf kmem' tool

>> TODO:
>> - show sym+offset in 'callsite' column
> 
> The way to print symbolic information for the 'callsite' column is to 
> fill in and walk the thread->DSO->symbol trees that all perf tools 
> maintain:
> 
> 	/* simplified, without error handling */
> 
> 	ip = event->ip.ip;
> 
> 	thread = threads__findnew(event->ip.pid);
> 
> 	map = thread__find_map(thread, ip);
> 
> 	ip = map->map_ip(map, ip); /* map absolute RIP into DSO-relative one */
> 
> 	sym = map__find_symbol(map, ip, symbol_filter);
> 
> then sym->name is the string that can be printed out. This works in a 
> symmetric way for both kernel-space and user-space symbols. (Call-chain 
> information can be captured and displayed too.)
> 
> ( 'Alloc Ptr' symbolization is harder, but it would be useful too i 
>   think, to map it back to the slab cache name. )
> 

Thanks.

I was lazy to figure it out by myself. ;)

>> - show cross node allocation stats
> 
> I checked and we appear to have all the right events for that - the node 
> ID is being traced consistently AFAICS.
> 

Actually kmemtrace-user shows this stats, but in a wrong way.
It doesn't map cpu_nr to node.

>> - collect more useful stats?
>> - ...
> 
> Pekka, Eduard and the other slab hackers might have ideas about what 
> other stats they generally like to see to judge the health of a workload 
> (or system).
> 
> If this iteration looks good to the slab folks then i can apply it as-is 
> and we can do the other changes relative to that. It looks good to me as 
> a first step, and it's functional already.
> 

Thanks!

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