Re: What's in linux-2.6-block.git for 2.6.24
From: Andrew Morton
Date: Fri Sep 21 2007 - 05:15:50 EST
On Fri, 21 Sep 2007 10:57:11 +0200 Jens Axboe <jens.axboe@xxxxxxxxxx> wrote:
> Hi,
>
> This details the contents of the block git repo of items that are bound
> for a 2.6.24 merge. The SCSI data buffer accessor patch from Tomo will
> also be going in through the block tree, but it's not merged up yet.
> That's mainly due to my laziness, not because the code isn't ready. That
> will happen sometime during today.
>
> Misc bits:
> - Various bug fixes from Neil Brown, part of his larger patchset for
> allowing arbitrarily sized bios.
> - Various little bug fixes and documentation updates.
>
> Barriers:
> - The empty bio barrier patches from me. These allow sending down a bio
> with no data attached, for insertion a barrier in a request queue.
> They are useful for dm and md, but also cleans up the sync
> blkdev_issue_flush() interface - it's now no longer an addon hack, but
> just a natural use of empty bio barriers.
That sounds useful.
> SG chaining bits:
> - This is the bulk of the patchset. It consists of three major
> components:
>
> - sglist-core, which add helpers for iterating sg lists and
> switches the block layer and SCSI to use those. Should not
> have any functional changes.
> - sglist-drivers, which converts drivers to use the sg list
> helpers. Again, should not contain functional changes.
> - sglist-arch, which adds support to most architectures and
> actually enables sg chaining.
>
> The goal of sg chaining is to allow support for very large sgtables,
> without requiring that they be allocated from one contigious piece of
> memory.
Presumably sg chaining means more overhead on the IO submission paths? If
so, has this been quantified?
-
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