On Apr 25, 2012, at 11:22 PM, Bean <bean12...@gmail.com> wrote:
> On Thu, Apr 26, 2012 at 12:10 PM, Seth Goldberg > <seth.goldb...@oracle.com> wrote: >> How does this work around the issue? I'm not seeing it -- we call SNP >> directly. We don't go through UDP or any other upper layers in efinet. >> When I did the investigation, I removed ALL other consumers of SNP manually >> via the efi shell before loading GRUB 2 and still saw packet loss. > > Hi, > > Normal OS has interrupt handler that removes the packet from nic > buffer as soon as possible, but grub2 is basically single thread and > use pull mode. So we should make the pulling loop as short as > possible. In async mode, if a packet is not found, it has to returned > to upper layer and retry, while in sync mode, the loop is inside the > driver which make it more efficient. It's something like reading 100 > bytes from disk is much faster than 100 x 1 byte. > Marginally. We still need to handle that packet inside grub once it is received. Besides, modern nic hardware has receive rings and overrun is rare especially with non-pipelined tftp (unless there is a ton of broadcast or unicast packets sent to the client while in grub which is unlikely in practice, so I'm not seeing where the real benefit is here. I can definitely understand your finding inefficiencies in the uefi udp-snp (or in systems I've seen it's more like UDP-MNP-SNP), so no argument there, but for grub 2, it's already using the lowest level interface it can (without calling undi directly). --S > > -- > Best wishes > Bean > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > https://lists.gnu.org/mailman/listinfo/grub-devel _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel