On Mon, Jan 14, 2013 at 11:28:19AM -0500, Benoit Jacob wrote: > 2013/1/14 Mike Hommey <m...@glandium.org> > > > On Mon, Jan 14, 2013 at 11:09:07AM -0500, Benoit Jacob wrote: > > > 2013/1/14 Mike Hommey <m...@glandium.org> > > > > > > > On Mon, Jan 14, 2013 at 11:43:44AM +1300, Robert O'Callahan wrote: > > > > > I need a big read-only buffer full of zeroes. On Linux I could mmap > > > > > /dev/zero read-only, and something similar on Windows/Mac I'm sure, > > but > > > > do > > > > > we already have code for that, or better yet something like that > > already > > > > > mapped into memory? > > > > > > > > You could just use calloc(). Jemalloc will do the appropriate thing. > > > > > > > > > > Out of curiosity, how can it? Since the block returned by calloc is not > > > read-only, how would a subsequent non-zero write be handled? > > > > It doesn't set it as read-only, so that depends if roc really needs the > > buffer to be read-only or not. > > > > I tried to ask a different question: > > Roc wants (IIUC) to allocate dummy zero pages that don't actually consume > memory. > > You propose (IIUC) that he use calloc() for that. > > My question, then, is: how could calloc() avoid actually allocating real > memory pages? If calloc() could know that these pages won't be written do, > it could map dummy zero pages, but AFAICS it can't know that...
It just maps anonymous memory (for big enough sizes), which is always initially zero pages. Mike _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
