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    Subject[PATCHv2 00/16] [FS, MM, block, MMC]: eMMC High Priority Interrupt Feature
    Standard eMMC (Embedded MultiMedia Card) specification expects to execute
    one request at a time. If some requests are more important than others, they
    can't be aborted while the flash procedure is in progress.

    New versions of the eMMC standard (4.41 and above) specfies a feature
    called High Priority Interrupt (HPI). This enables an ongoing transaction
    to be aborted using a special command (HPI command) so that the card is ready
    to receive new commands immediately. Then the new request can be submitted
    to the card, and optionally the interrupted command can be resumed again.

    Some restrictions exist on when and how the command can be used. For example,
    only write and write-like commands (ERASE) can be preempted, and the urgent
    request must be a read.

    In order to support this in software,
    a) At the top level, some policy decisions have to be made on what is
    worth preempting for.
    This implementation uses the demand paging requests and swap
    read requests as potential reads worth preempting an ongoing long write.
    This is expected to provide improved responsiveness for smarphones
    with multitasking capabilities - example would be launch a email application
    while a video capture session (which causes long writes) is ongoing.
    b) At the block handler, the higher priority request should be queued
    ahead of the pending requests in the elevator
    c) At the MMC block and core level, transactions have to executed to
    enforce the rules of the MMC spec and make a reasonable tradeoff if the
    ongoing command is really worth preempting. (For example, is it too close
    to completing already ?).
    The current implementation uses a fixed time logic. If 10ms has
    already elapsed since the first request was submitted, then a new high
    priority request would not cause a HPI, as it is expected that the first
    request would finish soon. Further work is needed to dynamically tune
    this value (maybe through sysfs) or automatically determine based on
    average write times of previous requests.
    d) At the lowest level (MMC host controllers), support interface to
    provide a transition path for ongoing transactions to be aborted and the
    controller to be ready to receive next command.

    More information about this feature can be found at
    Jedec Specification:-
    Presentation on eMMC4.41 features:-

    In no particular order, thanks to Arnd Bergmann and Saugata Das
    from Linaro, Ilan Smith and Alex Lemberg from Sandisk, Luca Porzio from Micron
    Technologies, Yejin Moon, Jae Hoon Chung from Samsung and others.

    v1 -> v2:-
    * Convert threshold for hpi usage to a tuning parameter (sysfs)
    * Add Documentation/ABI for all sysfs entries
    * Add implementation of abort for OMAP controller
    * Rebased to 3.4-rc4 + mmc-next

    This patch series depends on a few other related cleanups
    in MMC driver. All the patches and the dependent series can be
    pulled from
    git:// my/mmc/3.4/foreground-hpiv2

    Ilan Smith (3):
    FS: Added demand paging markers to filesystem
    MM: Added page swapping markers to memory management
    block: treat DMPG and SWAPIN requests as special

    Venkatraman S (13):
    block: add queue attributes to manage dpmg and swapin requests
    block: add sysfs attributes for runtime control of dpmg and swapin
    block: Documentation: add sysfs ABI for expedite_dmpg and expedite_swapin
    mmc: core: helper function for finding preemptible command
    mmc: core: add preemptibility tracking fields to mmc command
    mmc: core: Add MMC abort interface
    mmc: block: Detect HPI support in card and host controller
    mmc: core: Implement foreground request preemption procedure
    mmc: sysfs: Add sysfs entry for tuning preempt_time_threshold
    mmc: Documentation: Add sysfs ABI for hpi_time_threshold
    mmc: block: Implement HPI invocation and handling logic.
    mmc: Update preempted request with CORRECTLY_PRG_SECTORS_NUM info
    mmc: omap_hsmmc: Implement abort_req host_ops

    Documentation/ABI/testing/sysfs-block | 12 ++
    Documentation/ABI/testing/sysfs-devices-mmc | 12 ++
    block/blk-core.c | 18 +++
    block/blk-sysfs.c | 16 +++
    block/elevator.c | 14 ++-
    drivers/mmc/card/block.c | 143 ++++++++++++++++++++--
    drivers/mmc/card/queue.h | 1 +
    drivers/mmc/core/core.c | 67 ++++++++++
    drivers/mmc/core/mmc.c | 25 ++++
    drivers/mmc/host/omap_hsmmc.c | 55 ++++++++-
    fs/mpage.c | 2 +
    include/linux/bio.h | 8 ++
    include/linux/blk_types.h | 4 +
    include/linux/blkdev.h | 8 ++
    include/linux/mmc/card.h | 1 +
    include/linux/mmc/core.h | 19 +++
    include/linux/mmc/host.h | 1 +
    include/linux/mmc/mmc.h | 4 +
    mm/page_io.c | 3 +-
    19 files changed, 395 insertions(+), 18 deletions(-)


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