linux-kernel - Re: [PATCH v3 04/17] lib min_heap: Add type safe interface

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Message-ID: <Zh1lY8EFyE943+89@visitorckw-System-Product-Name>
Date: Tue, 16 Apr 2024 01:35:31 +0800
From: Kuan-Wei Chiu <visitorckw@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: colyli@...e.de, kent.overstreet@...ux.dev, msakai@...hat.com,
	mingo@...hat.com, acme@...nel.org, namhyung@...nel.org,
	akpm@...ux-foundation.org, bfoster@...hat.com, mark.rutland@....com,
	alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
	irogers@...gle.com, adrian.hunter@...el.com, jserv@...s.ncku.edu.tw,
	linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
	dm-devel@...ts.linux.dev, linux-bcachefs@...r.kernel.org,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v3 04/17] lib min_heap: Add type safe interface

On Fri, Apr 12, 2024 at 09:30:17AM +0200, Peter Zijlstra wrote:
> On Sun, Apr 07, 2024 at 12:47:14AM +0800, Kuan-Wei Chiu wrote:
> 
> > -struct min_heap {
> > -	void *data;
> > -	int nr;
> > -	int size;
> > -};
> > +#define MIN_HEAP_PREALLOCATED(_type, _name, _nr)	\
> > +struct _name {	\
> > +	int nr;	\
> > +	int size;	\
> > +	_type *data;	\
> > +	_type preallocated[_nr];	\
> > +}
> 
> 
> > @@ -3738,7 +3739,7 @@ static noinline int visit_groups_merge(struct perf_event_context *ctx,
> >  	struct perf_cpu_context *cpuctx = NULL;
> >  	/* Space for per CPU and/or any CPU event iterators. */
> >  	struct perf_event *itrs[2];
> > -	struct min_heap event_heap;
> > +	struct perf_event_min_heap event_heap;
> >  	struct perf_event **evt;
> >  	int ret;
> >  
> > @@ -3747,11 +3748,9 @@ static noinline int visit_groups_merge(struct perf_event_context *ctx,
> >  
> >  	if (!ctx->task) {
> >  		cpuctx = this_cpu_ptr(&perf_cpu_context);
> > -		event_heap = (struct min_heap){
> > -			.data = cpuctx->heap,
> > -			.nr = 0,
> > -			.size = cpuctx->heap_size,
> > -		};
> > +		event_heap.data = cpuctx->heap;
> > +		event_heap.nr = 0;
> > +		event_heap.size = cpuctx->heap_size;
> >  
> >  		lockdep_assert_held(&cpuctx->ctx.lock);
> >  
> > @@ -3760,11 +3759,9 @@ static noinline int visit_groups_merge(struct perf_event_context *ctx,
> >  			css = &cpuctx->cgrp->css;
> >  #endif
> >  	} else {
> > -		event_heap = (struct min_heap){
> > -			.data = itrs,
> > -			.nr = 0,
> > -			.size = ARRAY_SIZE(itrs),
> > -		};
> > +		event_heap.data = itrs;
> > +		event_heap.nr = 0;
> > +		event_heap.size = ARRAY_SIZE(itrs);
> >  		/* Events not within a CPU context may be on any CPU. */
> >  		__heap_add(&event_heap, perf_event_groups_first(groups, -1, pmu, NULL));
> >  	}
> 
> Not too happy about these. If you ever add more fields they will go
> uninitialized. Why not keep the existing form and fix the struct name?

Sorry for the late reply. I'm traveling.
I'll change that back in v4.

Regards,
Kuan-Wei