linux-kernel - Re: [PATCH RFC v3 07/35] mm: cma: Add CMA_RELEASE

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Date: Mon, 29 Jan 2024 11:53:23 +0000
From: Alexandru Elisei <alexandru.elisei@....com>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: catalin.marinas@....com, will@...nel.org, oliver.upton@...ux.dev,
	maz@...nel.org, james.morse@....com, suzuki.poulose@....com,
	yuzenghui@...wei.com, arnd@...db.de, akpm@...ux-foundation.org,
	mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
	bristot@...hat.com, vschneid@...hat.com, mhiramat@...nel.org,
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	eugenis@...gle.com, kcc@...gle.com, hyesoo.yu@...sung.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-mm@...ck.org,
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v3 07/35] mm: cma: Add CMA_RELEASE_{SUCCESS,FAIL}
 events

Hi,

On Mon, Jan 29, 2024 at 03:01:24PM +0530, Anshuman Khandual wrote:
> 
> 
> On 1/25/24 22:12, Alexandru Elisei wrote:
> > Similar to the two events that relate to CMA allocations, add the
> > CMA_RELEASE_SUCCESS and CMA_RELEASE_FAIL events that count when CMA pages
> > are freed.
> 
> How is this is going to be beneficial towards analyzing CMA alloc/release
> behaviour - particularly with respect to this series. OR just adding this
> from parity perspective with CMA alloc side counters ? Regardless this
> CMA change too could be discussed separately.

Added for parity and because it's useful for this series (see my reply to
the previous patch where I discuss how I've used the counters).

Thanks,
Alex

> 
> > 
> > Signed-off-by: Alexandru Elisei <alexandru.elisei@....com>
> > ---
> > 
> > Changes since rfc v2:
> > 
> > * New patch.
> > 
> >  include/linux/vm_event_item.h | 2 ++
> >  mm/cma.c                      | 6 +++++-
> >  mm/vmstat.c                   | 2 ++
> >  3 files changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> > index 747943bc8cc2..aba5c5bf8127 100644
> > --- a/include/linux/vm_event_item.h
> > +++ b/include/linux/vm_event_item.h
> > @@ -83,6 +83,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
> >  #ifdef CONFIG_CMA
> >  		CMA_ALLOC_SUCCESS,
> >  		CMA_ALLOC_FAIL,
> > +		CMA_RELEASE_SUCCESS,
> > +		CMA_RELEASE_FAIL,
> >  #endif
> >  		UNEVICTABLE_PGCULLED,	/* culled to noreclaim list */
> >  		UNEVICTABLE_PGSCANNED,	/* scanned for reclaimability */
> > diff --git a/mm/cma.c b/mm/cma.c
> > index dbf7fe8cb1bd..543bb6b3be8e 100644
> > --- a/mm/cma.c
> > +++ b/mm/cma.c
> > @@ -562,8 +562,10 @@ bool cma_release(struct cma *cma, const struct page *pages,
> >  {
> >  	unsigned long pfn;
> >  
> > -	if (!cma_pages_valid(cma, pages, count))
> > +	if (!cma_pages_valid(cma, pages, count)) {
> > +		count_vm_events(CMA_RELEASE_FAIL, count);
> >  		return false;
> > +	}
> >  
> >  	pr_debug("%s(page %p, count %lu)\n", __func__, (void *)pages, count);
> >  
> > @@ -575,6 +577,8 @@ bool cma_release(struct cma *cma, const struct page *pages,
> >  	cma_clear_bitmap(cma, pfn, count);
> >  	trace_cma_release(cma->name, pfn, pages, count);
> >  
> > +	count_vm_events(CMA_RELEASE_SUCCESS, count);
> > +
> >  	return true;
> >  }
> >  
> > diff --git a/mm/vmstat.c b/mm/vmstat.c
> > index db79935e4a54..eebfd5c6c723 100644
> > --- a/mm/vmstat.c
> > +++ b/mm/vmstat.c
> > @@ -1340,6 +1340,8 @@ const char * const vmstat_text[] = {
> >  #ifdef CONFIG_CMA
> >  	"cma_alloc_success",
> >  	"cma_alloc_fail",
> > +	"cma_release_success",
> > +	"cma_release_fail",
> >  #endif
> >  	"unevictable_pgs_culled",
> >  	"unevictable_pgs_scanned",