An unreceived message can have a reference to a master-allocated
value, in which case that value must be marked. This marking
is implemented by embedding a linked link within the message
memory.
This improvement applies to both poll() and select() modes, and it
can reduce scheduling overhead when blocking on many I/O sources
at once.
This mode is not enabled for Windows, however, since Racket doesn't
exactly use select() on Windows.
On Mac OS X, poll() doesn't work right in versions earlier than 10.5.5,
select() is always faster, and large number of sockets will be
better handled via kqueue(). On Linux, poll() is defintely better.
Otherwise, we stick with select() to be conservative.
Applies in the case of simple ports without line counting, etc.
Also, `read-line' keeps track of whether all bytes are ASCII
(which is easy) to shortcut general UTF-8 decoding.
On x86_64, if the scratch-space address fits into 32
bits and the final place for shared code doesn't
fit into a 32-bit address, then the size of the generated
code could change, leading to a JIT buffer overflow.
Merge to 5.2
Fix memory accounting to detect when messages pile up in a
place channel and when shared values (such as the result of
`make-shared-bytes') pile up. Also fix problems where a GC
or free-page purge needs to be triggered.
The implementation causes a minor API change, which is that
a place channel sent multiple times as a message generates
values that are `equal?' but no longer eq?'.
Closes PR 12273
[Do not merge to 5.2]
Reordering `unsafe-vector-ref' past an `unsafe-vector-set!' was
particularly bad. Meanwhile, some non-mutating operations like
`unsafe-mcar' were treated too conservatively.
Merge to 5.2
The bug was that a procedure could be incorrectly marked as
a "leaf" procedure, which could in turn cause the compiler
to keep inlining a very small procedure that calls itself.
Closes PR 12270
Merge to 5.2
