Re: return to the begin of InputStream
On 12/9/2009 4:13 PM, Tom Anderson wrote:
On Wed, 9 Dec 2009, Eric Sosman wrote:
On 12/9/2009 10:49 AM, Tom Anderson wrote:
On Sat, 5 Dec 2009, Eric Sosman wrote:
(Marginally topical) [...]
(The topicality margin gets even thinner) [...]
[...]
As for file modification times, I confess an incomplete grasp of
exactly which operations do and do not update them. However, just
poking a new value into a page that's mmap'ed from a file is not
enough to update the time stamp. Can you imagine the overhead if every
memory write trapped to the kernel to update the time?
Right, but the kernel could update the mtime when it flushed pages to
disk. The timestamp would reflect the time of the flush, not the write
to the page, but that's how it is with buffered stream IO too. Or am i
misunderstanding again, and there was no writing to disk happening?
(Topicality margin now thin enough to use in a microtome)
No disk writes. The tmpfs file system on Solaris tries to
stay memory-resident as much as possible, and only goes to the
swap area(s) if RAM becomes awfully scarce.
I take it you didn't have SysV shmget/shmat here?
Had 'em, sure, but the folks who wrote the application
chose not to use them. (Not by default, anyhow: There was a
way to use shm instead of /tmp files, but it involved some
serious headaches for the administrator of the application
and was seldom done.)
Anyhow, this has really strayed pretty far from Java. If
for some reason you're interested in pursuing it further, I
suggest you E-mail me and we'll take it off-line.
--
Eric Sosman
esosman@ieee-dot-org.invalid