[PATCH] drm/ttm: stop warning on TT shrinker failure

[Christian König]

Am 19.03.21 um 18:52 schrieb Daniel Vetter:
> On Fri, Mar 19, 2021 at 03:08:57PM +0100, Christian König wrote:
>> Don't print a warning when we fail to allocate a page for swapping things out.
>>
>> Also rely on memalloc_nofs_save/memalloc_nofs_restore instead of GFP_NOFS.
> Uh this part doesn't make sense. Especially since you only do it for the
> debugfs file, not in general. Which means you've just completely broken
> the shrinker.

Are you sure? My impression is that GFP_NOFS should now work much more 
out of the box with the memalloc_nofs_save()/memalloc_nofs_restore().

> If this is just to paper over the seq_printf doing the wrong allocations,
> then just move that out from under the fs_reclaim_acquire/release part.

No, that wasn't the problem.

We have just seen to many failures to allocate pages for swapout and I 
think that would improve this because in a lot of cases we can then 
immediately swap things out instead of having to rely on upper layers.

Regards,
Christian.


>
> __GFP_NOWARN should be there indeed I think.
> -Daniel
>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_tt.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
>> index 2f0833c98d2c..86fa3e82dacc 100644
>> --- a/drivers/gpu/drm/ttm/ttm_tt.c
>> +++ b/drivers/gpu/drm/ttm/ttm_tt.c
>> @@ -369,7 +369,7 @@ static unsigned long ttm_tt_shrinker_scan(struct shrinker *shrink,
>>   	};
>>   	int ret;
>>   
>> -	ret = ttm_bo_swapout(&ctx, GFP_NOFS);
>> +	ret = ttm_bo_swapout(&ctx, GFP_KERNEL | __GFP_NOWARN);
>>   	return ret < 0 ? SHRINK_EMPTY : ret;
>>   }
>>   
>> @@ -389,10 +389,13 @@ static unsigned long ttm_tt_shrinker_count(struct shrinker *shrink,
>>   static int ttm_tt_debugfs_shrink_show(struct seq_file *m, void *data)
>>   {
>>   	struct shrink_control sc = { .gfp_mask = GFP_KERNEL };
>> +	unsigned int flags;
>>   
>>   	fs_reclaim_acquire(GFP_KERNEL);
>> +	flags = memalloc_nofs_save();
>>   	seq_printf(m, "%lu/%lu\n", ttm_tt_shrinker_count(&mm_shrinker, &sc),
>>   		   ttm_tt_shrinker_scan(&mm_shrinker, &sc));
>> +	memalloc_nofs_restore(flags);
>>   	fs_reclaim_release(GFP_KERNEL);
>>   
>>   	return 0;
>> -- 
>> 2.25.1
>>
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