Make MAXPHYS tunable. Bump MAXPHYS to 1M.

Replace MAXPHYS by runtime variable maxphys. It is initialized from
MAXPHYS by default, but can be also adjusted with the tunable kern.maxphys.

Make b_pages[] array in struct buf flexible.  Size b_pages[] for buffer
cache buffers exactly to atop(maxbcachebuf) (currently it is sized to
atop(MAXPHYS)), and b_pages[] for pbufs is sized to atop(maxphys) + 1.
The +1 for pbufs allow several pbuf consumers, among them vmapbuf(),
to use unaligned buffers still sized to maxphys, esp. when such
buffers come from userspace (*).  Overall, we save significant amount
of otherwise wasted memory in b_pages[] for buffer cache buffers,
while bumping MAXPHYS to desired high value.

Eliminate all direct uses of the MAXPHYS constant in kernel and driver
sources, except a place which initialize maxphys.  Some random (and
arguably weird) uses of MAXPHYS, e.g. in linuxolator, are converted
straight.  Some drivers, which use MAXPHYS to size embeded structures,
get private MAXPHYS-like constant; their convertion is out of scope
for this work.

Changes to cam/, dev/ahci, dev/ata, dev/mpr, dev/mpt, dev/mvs,
dev/siis, where either submitted by, or based on changes by mav.

Suggested by: mav (*)
Reviewed by:	imp, mav, imp, mckusick, scottl (intermediate versions)
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
Differential revision:	https://reviews.freebsd.org/D27225

1 files changed, 1 insertions, 1 deletions

diff --git a/sys/dev/ahci/ahciem.c b/sys/dev/ahci/ahciem.c
index a6f22fac5639..b1c3fbf1fdd4 100644
--- a/sys/dev/ahci/ahciem.c
+++ b/sys/dev/ahci/ahciem.c
@@ -641,7 +641,7 @@ ahciemaction(struct cam_sim *sim, union ccb *ccb)
 		cpi->transport_version = XPORT_VERSION_UNSPECIFIED;
 		cpi->protocol = PROTO_ATA;
 		cpi->protocol_version = PROTO_VERSION_UNSPECIFIED;
-		cpi->maxio = MAXPHYS;
+		cpi->maxio = maxphys;
 		cpi->hba_vendor = pci_get_vendor(parent);
 		cpi->hba_device = pci_get_device(parent);
 		cpi->hba_subvendor = pci_get_subvendor(parent);