possible IO map leak in drm/gem

[Chuck Lever]

> On Jan 21, 2021, at 9:47 AM, Thomas Zimmermann <tzimmermann at suse.de> wrote:
> 
> (cc'ing dri-devel)
> 
> Hi,
> 
> thanks for reporting the bug.
> 
> Am 21.01.21 um 15:35 schrieb Chuck Lever:
>> Hi Thomas-
>> I was not able to find an appropriate mailing list entry in MAINTAINERS,
> 
> That would be dri-devel at lists.freedesktop.org
> 
>> so I'm mailing you directly as committer of record for:
>> 43676605f890 ("drm/ttm: Add vmap/vunmap to TTM and TTM GEM helpers")
>> I've noticed that since putting v5.11-rc on my test systems, overnight
>> on an otherwise idle system the load average seems to grow as the result
>> of a kernel worker thread.
> 
> Earlier this week I fixed a couple of leaks in that code. Could you please apply the patch at [1] and report back if it fixes the issue.
> 
> If it's a separate problem, I'll take a closer look.

Thomas, thank you for your quick response. I've installed your patch
on one system and it looks promising already. I'll let it soak overnight.


> Best regards
> Thomas
> 
> [1] https://lore.kernel.org/dri-devel/20210118144639.27307-1-tzimmermann@suse.de/
> 
>> I used "perf top" to see what it had gotten up to, and it appears that
>> it was spending lots of time walking an interval tree on behalf of
>> memtype_reserve().
>> The most frequently-observed stack trace seems to be:
>>      kworker/3:1-2355  [003] 60950.150928: function:             memtype_reserve
>>      kworker/3:1-2355  [003] 60950.150942: kernel_stack:         <stack trace>
>> => ffffffffc0c66083
>> => memtype_reserve (ffffffffa005f9d5)
>> => __ioremap_caller (ffffffffa005aac1)
>> => ttm_bo_vmap (ffffffffc040f266)
>> => drm_gem_vram_vmap (ffffffffc042c5cd)
>> => drm_gem_vmap (ffffffffc0506a7f)
>> => drm_client_buffer_vmap (ffffffffc0523741)
>> => drm_fb_helper_damage_work (ffffffffc049a34a)
>> => process_one_work (ffffffffa00dd92e)
>> => worker_thread (ffffffffa00dde46)
>> => kthread (ffffffffa00e22c4)
>> => ret_from_fork (ffffffffa0004192)
>> I see a regular call to memtype_reserve(), but never a matching call to
>> memtype_free(), thus I suspect a leak of I/O maps in this code.
>> --
>> Chuck Lever
> 
> -- 
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer

--
Chuck Lever