Annotation of wikisrc/projects/project/buffer-queue.mdwn, revision 1.3

1.1       jmmv        1: [[!template id=project
                      2: 
                      3: title="More intelligent buffer queue management"
                      4: 
                      5: contact="""
                      6: [tech-kern](mailto:tech-kern@NetBSD.org)
                      7: """
                      8: 
                      9: category="kernel"
1.2       jmmv       10: difficulty="medium"
1.1       jmmv       11: duration="2-3 months"
                     12: 
                     13: description="""
1.3     ! dholland   14: NetBSD has a fixed, kernel-wide upper limit on transfer size, called MAXPHYS, which is currently
        !            15: set to 64k on most ports.  This is too small to perform well on modern
1.1       jmmv       16: IDE and SCSI hardware; on the other hand some devices can't do more than 64k,
1.3     ! dholland   17: and in some cases are even limited to less (the Xen virtual block device for
1.1       jmmv       18: example).  Software RAID will also cause requests to be split in multiple
                     19: smaller requests.
                     20: 
1.3     ! dholland   21: There is currently work in progress to make MAXPHYS configured at
        !            22: runtime based on driver capability.
        !            23: 
        !            24: This project originaly suggested instead to make the buffer queue
        !            25: management logic (which currently only sorts the queue, aka disksort)
        !            26: capable of splitting too-large buffers or aggregating small contiguous
        !            27: buffers in order to conform to device-level requirements.
        !            28: 
        !            29: Once the MAXPHYS changes are finalized and committed, this project may
        !            30: be simply outdated. However, it may also be worthwhile to pursue this
        !            31: idea as well, particularly the aggregation part.
        !            32: 
1.1       jmmv       33: """
                     34: ]]

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