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From Cliff Woolley <cliffwool...@yahoo.com>
Subject Re: Buckets destroy not cleaning up private structures?
Date Mon, 30 Apr 2001 19:34:59 GMT
On Mon, 30 Apr 2001, Cliff Woolley wrote:

> This is definitely better than the leak.  =-)  And nothing says that the
> cache can't apr_mmap_delete() the MMAP associated with the master file
> bucket as long as refcount==1 (ie, there are no requests using that
> file/mmap currently in progress) if it decides it has too many MMAPs
> laying around.  It's possible that the file will be re-MMAPed by a later
> request, but the MMAPs could be just cycled through in an LRU fashion.
> This would leak one palloc'ed apr_mmap_t in the cache's pool, however.
> It's a trade-off.  Which is better: having potentially as many MMAPs open
> as you have file handles cached, or growing the size of the cache pool by
> sizeof(apr_mmap_t) each time you delete and recreate an MMAP for a file?
> In either case, this is still much better than the current situation (the
> leak), which has both problems, only worse...  ;-]

I had an idea for fixing the leaking of the apr_mmap_t structure at lunch,
and thought I'd throw it out here for discussion.

One way around this is to have a variant of apr_mmap_create() that accepts
an existing apr_mmap_t structure and "fills it out", rather than
preemptively palloc'ing a new apr_mmap_t and using that one.  If we had
that, then the apr_file_t could contain a pointer to the apr_mmap_t for
that file.  The first time the file is MMAP'ed, the apr_mmap_t that's
allocated is hung off the apr_file_t's pointer.  The apr_mmap_t has a flag
in it that indicates "active" or not.  When the mmap is apr_mmap_delete'd,
the flag is set inactive.  If the file gets re-MMAP'ed, the apr_mmap_t
created before is reused and set active again.

I don't know if this is useful or not, but it's one idea.  Just a thought.


   Cliff Woolley
   Charlottesville, VA

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