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Re: Grub2 EFI: Image loading from USB takes too long

From: Vladimir 'φ-coder/phcoder' Serbinenko
Subject: Re: Grub2 EFI: Image loading from USB takes too long
Date: Fri, 15 Apr 2011 08:55:47 +0200
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On 15.04.2011 04:45, Bean wrote:
> Hi,
> I believe this is caused by the read algorithm of grub2. If the file
> is continuous, grub legacy will read it in one pass, while grub2 will
> break it up into small blocks, this will slow it down dramatically. I
> haven't tested efi, but in bios mode, sometimes it takes twice as long
> for grub2 to read the same file.
That's why I asked which fs it is. On an FS like ext2 or fat Both GRUBs
are limited by the need of rereading indirect blocks or FAT chain (sure
this can be aleviated by buffering and merging the nodes but neither
GRUB Legacy nor GRUB2 does it). Currently it makes difference only on
extent-based filesystems like ext, xfs or btrfs. I don't want to embark
on adding another code path in grub_disk_read before having enough info
to confirm this theory yet neither the original reporter nor the others
answered which FS they conducted experiments on.

Vladimir 'φ-coder/phcoder' Serbinenko

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