stop using mmap for zip I/O

[Christos Zoulas]

On Mar 3,  2:41pm, dmitry.samersoff at oracle.com (Dmitry Samersoff) wrote:
-- Subject: Re: stop using mmap for zip I/O

| Christos,
| 
| JVM install it's own signal handler and use it to numerous tasks, so add
| signal handler to zip_util.c is problematic.

Yes, I understand; this is why I mentioned that we not change it
until the pure java implementation is released.

| The simplest way to address the problem is use mlock/munlock to test
| page presence before touching it.
| 
| i.e. add code like
| 
|      if ((i % 4096) == 0) {
|              if ( mlock(v+i, 4096) < 0) {
|                printf("No page. Bail out\n");
|                return;
|              }
|           }
| 
| to *compute()* in your example below.

Yes, that fixes it too, at the cost of more syscalls and complexity...
I just mentioned disable mmap, because it is easy and fixes a common
problem without any performance penalties. Perhaps the mmap code made
sense when it was mapping the whole file, but now mapping just the
central directory doesn't. (IMHO :-)

christos