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Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour
From: |
Seth Goldberg |
Subject: |
Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour |
Date: |
Wed, 25 Apr 2012 23:59:51 -0500 |
On Apr 25, 2012, at 11:22 PM, Bean <address@hidden> wrote:
> On Thu, Apr 26, 2012 at 12:10 PM, Seth Goldberg
> <address@hidden> 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
> address@hidden
> https://lists.gnu.org/mailman/listinfo/grub-devel
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, (continued)
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, Bean, 2012/04/25
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, Bean, 2012/04/25
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, Vladimir 'φ-coder/phcoder' Serbinenko, 2012/04/25
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, Bean, 2012/04/25
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, Seth Goldberg, 2012/04/26
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, Bean, 2012/04/26
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour,
Seth Goldberg <=
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, Bean, 2012/04/26
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, Seth Goldberg, 2012/04/26
- Re: RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour, Bean, 2012/04/26