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Fri, 15 Aug 2025 23:42:53 -0700 (PDT) Message-ID: <9be479a1-ab93-4ec7-b1aa-68acd94f15ea@gmail.com> Date: Sat, 16 Aug 2025 10:42:50 +0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/cma: print total and used pages in cma_alloc() To: David Hildenbrand , Xiang Gao , akpm@linux-foundation.org Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, gaoxiang17 References: <20250816042842.3959315-1-gxxa03070307@gmail.com> Content-Language: en-US From: Giorgi Tchankvetadze In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit What about using tracepoints? Add a trace_cma_alloc() event that only runs when tracing is enabled. No lock unless someone is actively monitoring On 8/16/2025 10:27 AM, David Hildenbrand wrote: > On 16.08.25 06:28, Xiang Gao wrote: >> From: gaoxiang17 >> >> This makes cma info more intuitive during debugging. >> >> before: >> [   24.407814] cma: cma_alloc(cma (____ptrval____), name: reserved, >> count 1, align 0) >> [   24.413397] cma: cma_alloc(cma (____ptrval____), name: reserved, >> count 1, align 0) >> [   24.415886] cma: cma_alloc(cma (____ptrval____), name: reserved, >> count 1, align 0) >> >> after: >> [   24.069738] cma: cma_alloc(cma (____ptrval____), name: reserved, >> total pages: 16384, used pages: 64, request pages: 1, align 0) >> [   24.075317] cma: cma_alloc(cma (____ptrval____), name: reserved, >> total pages: 16384, used pages: 65, request pages: 1, align 0) >> [   24.078455] cma: cma_alloc(cma (____ptrval____), name: reserved, >> total pages: 16384, used pages: 66, request pages: 1, align 0) >> >> Signed-off-by: gaoxiang17 >> --- >>   mm/cma.c | 15 +++++++++++++-- >>   1 file changed, 13 insertions(+), 2 deletions(-) >> >> diff --git a/mm/cma.c b/mm/cma.c >> index 2ffa4befb99a..46cc98e7f587 100644 >> --- a/mm/cma.c >> +++ b/mm/cma.c >> @@ -776,6 +776,17 @@ static void cma_debug_show_areas(struct cma *cma) >>       spin_unlock_irq(&cma->lock); >>   } >> +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); >> + >> +    return used << cma->order_per_bit; >> +} >> + >>   static int cma_range_alloc(struct cma *cma, struct cma_memrange *cmr, >>                   unsigned long count, unsigned int align, >>                   struct page **pagep, gfp_t gfp) >> @@ -858,8 +869,8 @@ static struct page *__cma_alloc(struct cma *cma, >> unsigned long count, >>       if (!cma || !cma->count) >>           return page; >> -    pr_debug("%s(cma %p, name: %s, count %lu, align %d)\n", __func__, >> -        (void *)cma, cma->name, count, align); >> +    pr_debug("%s(cma %p, name: %s, total pages: %lu, used pages: %lu, >> request pages: %lu, align %d)\n", >> +        __func__, (void *)cma, cma->name, cma->count, >> cma_get_used_pages(cma), count, align); > >         ^ one space missing for proper indentation. > > But doing another spinlock cycle just for debugging purposes? That does > not feel right, sorry. >