On Wed, 2007-03-28 at 00:28 +0200, Xavier Bestel wrote: > On mar, 2007-03-27 at 14:52 -0600, Federico Mena Quintero wrote:
> > [/me wonders if thumbnailers are measurably faster by using mmap() > > instead of read()...] > It depends on their access pattern. If they need sequential access, > read() is better because it can do prefetching (readahead). I think what Federico was getting at is that for most thumbnailers, rendering is likely to be a bigger bottleneck than I/O on a local file system. But we don't know this for sure until we've measured it. mmap() can do prefetching too - and it will likely load a 4k page at a time anyway. So I doubt prefetch plays a role in a comparison of read() and mmap(). I tend to favor read() on user data: - For robustness: An mmap() map can become invalid if the file is truncated, crashing the process. - Because mmap() makes your VSize - and with accesses, your RSS - grow correspondingly, with subsequent bug reports from irate users. -- Hans Petter _______________________________________________ desktop-devel-list mailing list [email protected] http://mail.gnome.org/mailman/listinfo/desktop-devel-list
