Справочник Пользователя для QLogic 7104-4M-CABLE
B–Write Combining
PAT and Write Combining
PAT and Write Combining
B-2
IB0056101-00 H
S
.
.
.
If you do not see any of these messages on your console, but suspect this
problem, check the /var/log/messages file. Some systems suppress driver
problem, check the /var/log/messages file. Some systems suppress driver
load messages but still output them to the log file.
Methods for enabling and disabling the two write combining mechanisms are
described in the following sections. There are no conflicts between the two
methods.
described in the following sections. There are no conflicts between the two
methods.
PAT and Write Combining
PAT is the default mechanism for allocating WC mappings for the PIO buffers. It is
set as a parameter in /etc/modprobe.conf (on Red Hat systems) or
/etc/modprobe.conf.local (on SLES systems). The default is:
set as a parameter in /etc/modprobe.conf (on Red Hat systems) or
/etc/modprobe.conf.local (on SLES systems). The default is:
option ib_ipath wc_pat=1
If PAT is unavailable or PAT initialization fails, the code generates a message in
the log and falls back to the MTRR mechanism. To use MTRR, disable PAT by
setting this module parameter to 0 (as a root user):
the log and falls back to the MTRR mechanism. To use MTRR, disable PAT by
setting this module parameter to 0 (as a root user):
option ib_ipath wc_pat=0
Then, revert to using the MTRR-only behavior by following one of the two
suggestions in
suggestions in
The driver will need to be restarted after the changes have been made.
MTRR Mapping and Write Combining
The following sections describe two methods for fixing MTRR issues.
See the Troubleshooting section of the QLogic Host Channel Adapter and QLogic
OFED Software Users Guide for more details on a related performance issue.
OFED Software Users Guide for more details on a related performance issue.
Edit BIOS Settings to Fix MTRR Issues
You can edit the BIOS setting for MTRR mapping. The BIOS setting looks similar
to:
to:
MTRR Mapping [Discrete]
NOTE:
There is no WC entry in /proc/mtrr when using PAT.