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
- Add a quirk to allow ignoring e820 extended memory detection.
- Improve memory detection through e801.
- Add bootloader command "biosmem".
See differential revision for more details.
Reviewed by: jhb, adrian
Approved by: adrian
Differential Revision: https://reviews.freebsd.org/D1741
heap when using a range above 1MB.
Previously the loader would always use the last 3MB in the first memory
range above 1MB for the heap. However, this memory range is also where the
kernel and any modules are loaded. If this memory range is "small", then
using the high 3MB for the heap may not leave enough room for the kernel
and modules.
Now the loader will use any range below 4GB for the heap, and the logic to
choose the "high" heap region has moved into biosmem.c. It sets two
variables that the loader can use for a high heap if it desires. When a
high heap is enabled (BZIP2, FireWire, GPT, or ZFS), then the following
memory ranges are preferred for the heap in order from best to worst:
- The largest memory region in the SMAP with a start address greater than
1MB. The memory region must be at least 3MB in length. This leaves the
region starting at 1MB purely for use by the kernel and modules.
- The last 3MB of the memory region starting at 1MB if it is at least 3MB
in size. This matches the current behavior except that the current loader
would break horribly if the first region was not at least 3MB in size.
- The memory range from the end of the loader up to the 640k window. This
is the range the loader uses when none of the high-heap-requesting options
are enabled.
Tested by: hrs
MFC after: 1 week
3MB of physical memory for heap instead of range between 1MB and 4MB.
This makes this feature working with PAE and amd64 kernels, which are
loaded at 2MB. Teach i386_copyin() to avoid using range allocated by
heap in such case, so that it won't trash heap in the low memory
conditions.
This should make loading bzip2-compressed kernels/modules/mfs images
generally useable, so that re@ team is welcome to evaluate merits
of using this feature in the installation CDs.
Valuable suggestions by: jhb
for our use. Use the same search order for BIOS memory size functions
as the kernel will later use.
Allow the loader to use all of the detected physical memory (this will
greatly help people trying to load enormous memory disk images).
More correctly handle running out of memory when loading an object.
Use the end of base memory for the top of the heap, rather than
blindly hoping that there is 384k left.
Add copyrights to a couple of files I forgot.
- Discard large amounts of BIOS-related code in favour of the more compact
BTX vm86 interface.
- Build the loader module as ELF, although the resulting object is a.out,
make gensetdefs 32/64-bit sensitive and use a single copy of it.
- Throw away installboot, as it's no longer required.
- Use direct bcopy operations in the i386_copy module, as BTX
maps the first 16M of memory. Check operations against the
detected size of actual memory.
