Hugetlbfs file mappings are handled differently than regular files:
- pager_req_create will tell us the file is in a hugetlbfs
- allocate memory upfront, we need to fail if not enough memory
- the memory needs to be given again if another process maps the same
file
This implementation still has some hacks, in particular, the memory
needs to be freed when all mappings are done and the file has been
deleted/closed by all processes.
We cannot know when the file is closed/unlinked easily, so clean up
memory when all processes have exited.
To test, install libhugetlbfs and link a program with the additional
LDFLAGS += -B /usr/share/libhugetlbfs -Wl,--hugetlbfs-align
Then run with HUGETLB_ELFMAP=RW set, you can check this works with
HUGETLB_DEBUG=1 HUGETLB_VERBOSE=2
Change-Id: I327920ff06efd82e91b319b27319f41912169af1
GCC optimizes big switches with sse so we could clobber users floating
point registers when they would do a syscall
Reproducer:
```
#include <stdio.h>
#include <stdlib.h>
union num {
float f;
unsigned long long i;
};
#define WORKSIZE (1024 * 1024 * 32)
int main(int argc, char **argv) {
char *work = malloc(WORKSIZE);
char *fromaddr;
char sink;
union num r;
unsigned long long int offset;
r.f = drand48();
printf("r: %llx\n", (long long)r.i);
offset = (long long int)(r.f * (double)WORKSIZE);
fromaddr = work + offset;
printf("%e %llx %llx\n", r.f, offset, fromaddr);
sink = *fromaddr;
return 0;
}
```
Change-Id: I7bb0883ec8ef2f245ab98064e308025422afc115
- make should be $(MAKE)
- add + in front of rules spawning long-lasted make process in a
subshell. (This would not be needed with $(MAKE) -C .. target, but our
makefiles do not handle that because they use $(PWD))
- split the main 'all' rule as all 4 targets are independant
- fix dependencies where appropriate for parallelism
Extra, not speed-related changes:
- remove some double-colon for targets as they do not need it
This cuts build time from 5s to 1.5s on a laptop with -j4, and more
importantly from 85s to 35s on a KNL node.
As a bonus, the fixed dependencies removes the need to clean before
rebuilding all the time. Probably.
