linux-kernel - 回复: 回复: [External Mail]Re: [PATCH v2] mm/cma: print total and used count in cma

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Message-ID: <65ba1fbcceb64cbdbf33b42787b447e9@xiaomi.com>
Date: Tue, 8 Oct 2024 02:13:17 +0000
From: 高翔 <gaoxiang17@...omi.com>
To: Frank van der Linden <fvdl@...gle.com>, Andrew Morton
	<akpm@...ux-foundation.org>
CC: David Hildenbrand <david@...hat.com>, Xiang Gao <gxxa03070307@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: 回复: 回复: [External Mail]Re: [PATCH v2] mm/cma: print total and used count in cma_alloc()


-----邮件原件-----
发件人: Frank van der Linden <fvdl@...gle.com> 
发送时间: 2024年10月5日 6:56
收件人: Andrew Morton <akpm@...ux-foundation.org>
抄送: 高翔 <gaoxiang17@...omi.com>; David Hildenbrand <david@...hat.com>; Xiang Gao <gxxa03070307@...il.com>; linux-mm@...ck.org; linux-kernel@...r.kernel.org
主题: Re: 回复: [External Mail]Re: [PATCH v2] mm/cma: print total and used count in cma_alloc()

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On Fri, Oct 4, 2024 at 3:39 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Fri, 4 Oct 2024 12:23:30 +0000 高翔 <gaoxiang17@...omi.com> wrote:
>
> > > > +static unsigned long cma_get_used_pages(struct cma *cma) {
> > > > +     unsigned long used;
> > > > +
> > > > +     spin_lock_irq(&cma->lock);
> > > > +     used = bitmap_weight(cma->bitmap, (int)cma_bitmap_maxno(cma));
> > > > +     spin_unlock_irq(&cma->lock);
> > >
> > > This adds overhead to each allocation, even if debug outputs are 
> > > ignored I assume?
> > >
> > > I wonder if we'd want to print these details only when our 
> > > allocation failed?
> > >
> > > Alternatively, we could actually track how many pages are 
> > > allocated in the cma, so we don't have to traverse the complete 
> > > bitmap on every allocation.
> > >
> >
> > Yep, that's what I did as part of
> > https://lore.kernel.org/all/20240724124845.614c03ad39f8af3729cebee6@
> > linux-foundation.org/T/
> >
> > That patch didn't make it in (yet). I'm happy for it to be combined with this one if that's easier.
>
> That patch has been forgotten about.  As I asked in July, "I suggest a 
> resend, and add some Cc:s for likely reviewers."

> Indeed - I certainly wasn't suggesting that anyone else forgot about it, it's up to me to follow up here, and I haven't yet.

For now, it's better to add members to "struct cma". Do I need to change it again?