On Wed, Mar 8, 2023 at 1:23 PM Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > On Wed, Mar 08, 2023 at 12:02:42PM -0800, Abhinav Kumar wrote: > > For DRM property blobs created by user mode using > > drm_property_create_blob(), if the blob value needs to be updated the > > only way is to destroy the previous blob and create a new one instead. > > > > For some of the property blobs, if the size of the blob is more > > than one page size, kvzalloc() can slow down system as it will first > > try to allocate physically contiguous memory but upon failure will > > fall back to non-contiguous (vmalloc) allocation. > > > > If the blob property being used is bigger than one page size, in a > > heavily loaded system, this causes performance issues because > > some of the blobs are updated on a per-frame basis. > > > > To mitigate the performance impact of kvzalloc(), use it only when > > the size of allocation is less than a page size when creating property > > blobs > > Not sure how badly this will eat into the vmalloc area. Normally I wouldn't expect this to be much of a problem, but we don't appear to restrict CREATEBLOBPROP to DRM_MASTER, which seems like it might have been a mistake.. so perhaps we want to either restrict CREATEBLOBPROP or put an upper threshold limit on total size of all allocated blob props using vmalloc area? BR, -R > Is there no GFP flag to avoid the expensive stuff instead? > > > > > Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> > > --- > > drivers/gpu/drm/drm_property.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/drm_property.c b/drivers/gpu/drm/drm_property.c > > index dfec479830e4..40c2a3142038 100644 > > --- a/drivers/gpu/drm/drm_property.c > > +++ b/drivers/gpu/drm/drm_property.c > > @@ -561,7 +561,11 @@ drm_property_create_blob(struct drm_device *dev, size_t length, > > if (!length || length > INT_MAX - sizeof(struct drm_property_blob)) > > return ERR_PTR(-EINVAL); > > > > - blob = kvzalloc(sizeof(struct drm_property_blob)+length, GFP_KERNEL); > > + if (sizeof(struct drm_property_blob) + length > PAGE_SIZE) > > + blob = vzalloc(sizeof(struct drm_property_blob)+length); > > + else > > + blob = kvzalloc(sizeof(struct drm_property_blob)+length, GFP_KERNEL); > > + > > if (!blob) > > return ERR_PTR(-ENOMEM); > > > > -- > > 2.7.4 > > -- > Ville Syrjälä > Intel
