linux-kernel - Re: [External] [PATCH v3] dma-buf: Add DmaBufTotal counter in meminfo

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Message-ID: <6de29664-bd8d-b744-2222-3c56cbf8a2e1@sony.com>
Date:   Sat, 17 Apr 2021 09:28:13 +0000
From:   <Peter.Enderborg@...y.com>
To:     <songmuchun@...edance.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <sumit.semwal@...aro.org>, <christian.koenig@....com>,
        <adobriyan@...il.com>, <akpm@...ux-foundation.org>, <guro@...com>,
        <shakeelb@...gle.com>, <mhocko@...e.com>, <neilb@...e.de>,
        <samitolvanen@...gle.com>, <rppt@...nel.org>,
        <linux-media@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linaro-mm-sig@...ts.linaro.org>, <willy@...radead.org>
Subject: Re: [External] [PATCH v3] dma-buf: Add DmaBufTotal counter in meminfo

On 4/17/21 5:05 AM, Muchun Song wrote:
> On Sat, Apr 17, 2021 at 12:08 AM Peter Enderborg
> <peter.enderborg@...y.com> wrote:
>> This adds a total used dma-buf memory. Details
>> can be found in debugfs, however it is not for everyone
>> and not always available. dma-buf are indirect allocated by
>> userspace. So with this value we can monitor and detect
>> userspace applications that have problems.
> I want to know more details about the problems.
> Can you share what problems you have encountered?
>
> Thanks.

What do you expect to be relevant for the kernel? Applications that leaks
is not that important. This types of buffers are important for android
applications, and android have moved a from ION buffers that has
metrics. It easily get in to 5-10 percent of the total amount ram.

This provide that information for end users or application developers
using commercial devices.  The end user get to know why their device
is running out of memory.


>> Signed-off-by: Peter Enderborg <peter.enderborg@...y.com>
>> ---
>>  drivers/dma-buf/dma-buf.c | 12 ++++++++++++
>>  fs/proc/meminfo.c         |  5 ++++-
>>  include/linux/dma-buf.h   |  1 +
>>  3 files changed, 17 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
>> index f264b70c383e..d40fff2ae1fa 100644
>> --- a/drivers/dma-buf/dma-buf.c
>> +++ b/drivers/dma-buf/dma-buf.c
>> @@ -37,6 +37,7 @@ struct dma_buf_list {
>>  };
>>
>>  static struct dma_buf_list db_list;
>> +static atomic_long_t dma_buf_global_allocated;
>>
>>  static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen)
>>  {
>> @@ -79,6 +80,7 @@ static void dma_buf_release(struct dentry *dentry)
>>         if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
>>                 dma_resv_fini(dmabuf->resv);
>>
>> +       atomic_long_sub(dmabuf->size, &dma_buf_global_allocated);
>>         module_put(dmabuf->owner);
>>         kfree(dmabuf->name);
>>         kfree(dmabuf);
>> @@ -586,6 +588,7 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
>>         mutex_lock(&db_list.lock);
>>         list_add(&dmabuf->list_node, &db_list.head);
>>         mutex_unlock(&db_list.lock);
>> +       atomic_long_add(dmabuf->size, &dma_buf_global_allocated);
>>
>>         return dmabuf;
>>
>> @@ -1346,6 +1349,15 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map)
>>  }
>>  EXPORT_SYMBOL_GPL(dma_buf_vunmap);
>>
>> +/**
>> + * dma_buf_get_size - Return the used nr pages by dma-buf
>> + */
>> +long dma_buf_allocated_pages(void)
>> +{
>> +       return atomic_long_read(&dma_buf_global_allocated) >> PAGE_SHIFT;
>> +}
>> +EXPORT_SYMBOL_GPL(dma_buf_allocated_pages);
> Why need "EXPORT_SYMBOL_GPL"?
This what all other exported functions for this module are. I don't see any reason for this do be different.
>
>> +
>>  #ifdef CONFIG_DEBUG_FS
>>  static int dma_buf_debug_show(struct seq_file *s, void *unused)
>>  {
>> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
>> index 6fa761c9cc78..ccc7c40c8db7 100644
>> --- a/fs/proc/meminfo.c
>> +++ b/fs/proc/meminfo.c
>> @@ -16,6 +16,7 @@
>>  #ifdef CONFIG_CMA
>>  #include <linux/cma.h>
>>  #endif
>> +#include <linux/dma-buf.h>
>>  #include <asm/page.h>
>>  #include "internal.h"
>>
>> @@ -145,7 +146,9 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>>         show_val_kb(m, "CmaFree:        ",
>>                     global_zone_page_state(NR_FREE_CMA_PAGES));
>>  #endif
>> -
>> +#ifdef CONFIG_DMA_SHARED_BUFFER
>> +       show_val_kb(m, "DmaBufTotal:    ", dma_buf_allocated_pages());
>> +#endif
>>         hugetlb_report_meminfo(m);
>>
>>         arch_report_meminfo(m);
>> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
>> index efdc56b9d95f..5b05816bd2cd 100644
>> --- a/include/linux/dma-buf.h
>> +++ b/include/linux/dma-buf.h
>> @@ -507,4 +507,5 @@ int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
>>                  unsigned long);
>>  int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
>>  void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
>> +long dma_buf_allocated_pages(void);
>>  #endif /* __DMA_BUF_H__ */
>> --
>> 2.17.1
>>