On Mon, Feb 19, 2024 at 02:34:42AM +0000, Ni, Ray wrote:
> > + for (GuidHob = GetFirstGuidHob (&mMpHandOffGuid);
> > + GuidHob != NULL;
> > + GuidHob = GetNextGuidHob (&mMpHandOffGuid, GET_NEXT_HOB
> > (GuidHob)))
> > + {
> > MpHandOff = (MP_HAND_OFF *)GET_GUID_HOB_DATA (GuidHob);
> > + if (MpHandOff->ProcessorIndex == ProcessorIndex) {
> > + return MpHandOff;
> > + }
>
> Gerd,
> The code is doing correctly but I have concerns about the performance impact.
>
> With the prototype GetMpHandOffHob(), callers call it multiple times to
> enumerate all HOB instances.
>
> But every call is a HOB list enumeration from top of the HOB list which may
> be slow in a platform
> that contains lots of HOB items and the MpHandOff HOB instances happen to be
> in the very bottom.
>
> How about add another parameter "HobStart" to GetMpHandOffHob()? So that only
> the first call to
> GetMpHandOffHob() is a HOB list enumeration from top, latter calls start from
> the next HOB of the previous
> found MpHandOff HOB instance.
That will only work if the HOBs are returned in ProcessorIndex order.
That happens to be the case in my testing; the HOBs are returned in the
same order they are created by patch #5 of this series.
Is that behavior guaranteed? MdePkg/Include/Library/HobLib.h doesn't
say anything about the ordering.
take care,
Gerd
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