On Tue, Apr 20, 2021 at 09:26:00AM +0000, peter.enderb...@sony.com wrote:
> On 4/20/21 10:58 AM, Daniel Vetter wrote:
> > On Sat, Apr 17, 2021 at 06:38:35PM +0200, Peter Enderborg 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.
> >>
> >> Signed-off-by: Peter Enderborg <peter.enderb...@sony.com>
> > So there have been tons of discussions around how to track dma-buf and
> > why, and I really need to understand the use-cass here first I think. proc
> > uapi is as much forever as anything else, and depending what you're doing
> > this doesn't make any sense at all:
> >
> > - on most linux systems dma-buf are only instantiated for shared buffer.
> > So there this gives you a fairly meaningless number and not anything
> > reflecting gpu memory usage at all.
> >
> > - on Android all buffers are allocated through dma-buf afaik. But there
> > we've recently had some discussions about how exactly we should track
> > all this, and the conclusion was that most of this should be solved by
> > cgroups long term. So if this is for Android, then I don't think adding
> > random quick stop-gaps to upstream is a good idea (because it's a pretty
> > long list of patches that have come up on this).
> >
> > So what is this for?
>
> For the overview. dma-buf today only have debugfs for info. Debugfs
> is not allowed by google to use in andoid. So this aggregate the information
> so we can get information on what going on on the system.
>
> And the LKML standard respond to that is "SHOW ME THE CODE".
Yes. Except this extends to how exactly this is supposed to be used in
userspace and acted upon.
> When the top memgc has a aggregated information on dma-buf it is maybe
> a better source to meminfo. But then it also imply that dma-buf requires
> memcg.
>
> And I dont see any problem to replace this with something better with it is
> ready.
The thing is, this is uapi. Once it's merged we cannot, ever, replace it.
It must be kept around forever, or a very close approximation thereof. So
merging this with the justification that we can fix it later on or replace
isn't going to happen.
-Daniel
>
> > -Daniel
> >
> >> ---
> >> 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..4dc37cd4293b 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_allocated_pages - Return the used nr of pages
> >> + * allocated for dma-buf
> >> + */
> >> +long dma_buf_allocated_pages(void)
> >> +{
> >> + return atomic_long_read(&dma_buf_global_allocated) >> PAGE_SHIFT;
> >> +}
> >> +
> >> #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
> >>
> >> _______________________________________________
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> >>
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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