[PATCH 00/33] SG table chaining support

Hi,

A repost of this patchset, which adds support forchaining of sg tables.
This enables much larger IO commands, since we don't have to allocate
large consecutive pieces of memory to represent the sgtable of a
huge command. Right now Linux is limited to somewhere between 128 and 256
segments, depending on the architecture. This translates into at most
512k-1mb request sizes. With this patchset, I've successfully pushed
10MiB commands through the IO stack.

This will potentially increase performance a lot on hardware that
requires larger IO commands to perform at their maximum.

Also see http://marc.info/?l=linux-kernel&m=117869783524152

To enable large IO commands for device sda, you would do:

# cd /sys/block/sda/queue
# echo 4096 > max_segments
# cat max_hw_sectors_kb  > max_sectors_kb

cat max_hw_sectors_kb to see what your largest IO size would now be.

Changes since last post:

- Rebase to current -git. Lots of SCSI drivers have been converted
  to use the sg accessor helpers, which nicely shrinks this patchset
  from 70 to 33 patches. Great!

-- 
Jens Axboe



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• Follow-Ups:
  • Re: [PATCH 00/33] SG table chaining support
    • From: "John Stoffel" <[email protected]>
  • Re: [PATCH 00/33] SG table chaining support
    • From: FUJITA Tomonori <[email protected]>
  • Re: [PATCH 00/33] SG table chaining support
    • From: FUJITA Tomonori <[email protected]>
  • [PATCH 05/33] Add chained sg support to linux/scatterlist.h
    • From: Jens Axboe <[email protected]>
  • [PATCH 06/33] i386 dma_map_sg: convert to using sg helpers
    • From: Jens Axboe <[email protected]>
  • [PATCH 07/33] i386: enable sg chaining
    • From: Jens Axboe <[email protected]>
  • [PATCH 20/33] scsi generic: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 12/33] PPC: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 13/33] SPARC: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 09/33] x86-64: update iommu/dma mapping functions to sg helpers
    • From: Jens Axboe <[email protected]>
  • [PATCH 17/33] ll_rw_blk: temporarily enable max_segments tweaking
    • From: Jens Axboe <[email protected]>
  • [PATCH 16/33] SCSI: support for allocating large scatterlists
    • From: Jens Axboe <[email protected]>
  • [PATCH 11/33] IA64: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 19/33] scsi_debug: support sg chaining
    • From: Jens Axboe <[email protected]>
  • [PATCH 10/33] x86-64: enable sg chaining
    • From: Jens Axboe <[email protected]>
  • [PATCH 14/33] SPARC64: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 15/33] scsi: simplify scsi_free_sgtable()
    • From: Jens Axboe <[email protected]>
  • [PATCH 18/33] libata: convert to using sg helpers
    • From: Jens Axboe <[email protected]>
  • [PATCH 21/33] qla1280: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 24/33] ide-scsi: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 23/33] qlogicpti: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 26/33] aha1542: convert to use the data buffer accessors
    • From: Jens Axboe <[email protected]>
  • [PATCH 32/33] i2o: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 30/33] USB storage: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 27/33] advansys: convert to use the data buffer accessors
    • From: Jens Axboe <[email protected]>
  • [PATCH 33/33] IDE: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 29/33] infiniband: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 22/33] aic94xx: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 28/33] ia64 simscsi: convert to use data buffer accessors
    • From: Jens Axboe <[email protected]>
  • [PATCH 31/33] Fusion: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 25/33] gdth: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 08/33] swiotlb: sg chaining support
    • From: Jens Axboe <[email protected]>
  • [PATCH 04/33] scsi: convert to using sg helpers
    • From: Jens Axboe <[email protected]>
  • [PATCH 03/33] block: convert to using sg helpers
    • From: Jens Axboe <[email protected]>
  • [PATCH 02/33] Add sg helpers for iterating over a scatterlist table
    • From: Jens Axboe <[email protected]>
  • [PATCH 01/33] crypto: don't pollute the global namespace with sg_next()
    • From: Jens Axboe <[email protected]>

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