The block cache implementation in loader has proven to be almost useless, and in worst case even slowing down the disk reads due to insufficient cache size and extra memory copy.
Also the current cache implementation does not cache reads from CDs, or work with zfs built on top of multiple disks.
Instead of an LRU, this code uses a simple hash (O(1) read from cache), and instead of a single global cache, a separate cache per block device.
The cache also implements limited read-ahead to increase performance.
To simplify read ahead management, the read ahead will not wrap over bcache end, so in worst case, single block physical read will be performed to fill the last block in bcache.
Booting from a virtual CD over IPMI:
0ms latency, before: 27 second, after: 7 seconds
60ms latency, before: over 12 minutes, after: under 5 minutes.
Submitted by: Toomas Soome <tsoome@me.com>
Reviewed by: delphij (previous version), emaste (previous version)
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D4713
There have been .local version of each for user modifications for some time
This allows users to receive future updates to these files
PR: 183765
Submitted by: Bertram Scharpf, Nikolai Lifanov (patch)
Reviewed by: dteske, loos, eadler
Approved by: bapt (mentor)
MFC after: 1 month
Relnotes: yes
Sponsored by: ScaleEngine Inc.
Differential Revision: https://reviews.freebsd.org/D3176
loader on PS3 and POWER8 systems. This is reasonably portable to other
architectures, especially FDT-based ones, if similar features are useful
elsewhere.
Netboot support is missing for now and will be added in a future commit,
at which time loader.ps3 will be garbage collected.
Done at: Hackathon
