On Wed, 2011-12-14 at 12:29 -0600, David Boyes wrote: > > I can easily replace the mmap-memcpy with pread/pwrite. Unfortunately I > > see huge performance drops if I do so. Currently I'm looking why the system > > call variant costs so much more than mmap. > > An alternative approach would be to mmap *only* the minidisk label and FST on > access of the minidisk, and then mmap individual files as you need them. I'm > not objecting to the use of mmap, just the gratuitous use of mmap on the > whole disk rather than what you actually *need* at that moment.
No, that wont work, files and the FST (also the allocation map) can be spread across any blocks of the disk. And mmap'ing single blocks together is complex and not worth the effort. Please see the other thread for my proposal... Jan > It's like the old Antonin Chekov quote about what's necessary in a play: if > there's a pistol on stage, you need to have killed someone by act II, scene > 1. Otherwise, take it out -- it didn't need to be there. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
