Lev Serebryakov wrote: > I'm digging thought GEOM/IO code and can not find place, where > requests from userland to read more than MAXPHYS bytes, is splitted > into several "struct bio"? > > It seems, that these children request are issued one-by-one, not in > parallel, am I right? Why? It breaks down parallelism, when > underlying GEOM can process several requests simoltaneously?
AFAIK first time requests from user-land broken to MAXPHYS-size pieces by physio() before entering GEOM. Requests are indeed serialized here, I suppose to limit KVA that thread can harvest, but IMHO it could be reconsidered. One more split happens (when needed) at geom_disk module to honor disk driver's maximal I/O size. There is no serialization. Most of ATA/SATA drivers in 8-STABLE support I/O up to at least min(512K, MAXPHYS) - 128K by default. Many SCSI drivers still limited by DFLTPHYS - 64K. -- Alexander Motin _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
