Who is the owner of the MNP component? (Or, put another way, if I submit a
patch to change this PaddingSize value, who will review it?)
The per-package owner list is not particularly helpful for components that
reside in MdeModulePkg since I'm assuming that there isn't just one developer
that is responsible for all of these components.
From: Cohen, Eugene
Sent: Monday, August 19, 2013 1:56 PM
To: edk2-devel@lists.sourceforge.net
Subject: [edk2] MNP PaddingSize Question
I've been tracking down a performance issue and have isolated it to this piece
of MNP initialization code:
//
// Make sure the protocol headers immediately following the media header
// 4-byte aligned, and also preserve additional space for VLAN tag
//
MnpDeviceData->PaddingSize = ((4 - SnpMode->MediaHeaderSize) & 0x3) +
NET_VLAN_TAG_LEN;
On my system this is coming up with '6' (MediaHeaderSize = 0xE) which is
causing performance issues since some of the memory copies to the resulting
non-dword aligned addresses are slower. As an experiment I tried bumping this
number to '8' and things worked well.
This value is used later when NET_BUFs are being allocated:
if (MnpDeviceData->PaddingSize > 0) {
//
// Pad padding bytes before the media header
//
NetbufAllocSpace (Nbuf, MnpDeviceData->PaddingSize, NET_BUF_TAIL);
NetbufTrim (Nbuf, MnpDeviceData->PaddingSize, NET_BUF_HEAD);
}
Can someone explain the purpose of PaddingSize and how that affects the later
processing of packets? Is this number a minimum value and is ok to be larger?
Thanks,
Eugene
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