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HP-UX Reference > S
swapctl(2)HP-UX 11i Version 3: February 2007 |
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NAMEswapctl — manage and configure system swap space PARAMETERS
DESCRIPTIONThe swapctl() system call manages system swap space by adding or deleting swap resources or returning information about swap resources. The cmd parameter determines the value of the arg parameter. Each of these commands accepts/returns information in a structure pointed to by the arg parameter. The following sections discuss the information that should be passed in to the system call. They also explain the information contained in these structures after a successful return. The SC_ADD CommandFor the SC_ADD command, arg parameter is a pointer to the swapres structure with some of the following members, depending on which type of swap is being configured: swapctl_flags_t sr_flag char * sr_name int64_t sr_start int64_t sr_length int64_t sr_priority int64_t sr_min int64_t sr_lim int64_t sr_res where the fields are as follows:
For the SC_ADD command, depending on the sr_flag type, the following members of swapres structure need to be passed in. SW_PRIMARY | SW_NEXTBOOT: *sr_name, sr_priority, sr_start, sr_length SW_DEVICE: *sr_name, sr_priority, sr_start, sr_length SW_FILESYS: *sr_name, sr_priority, sr_min, sr_lim, sr_res The SW_PRIMARY | SW_NEXTBOOT flag is used to change the primary swap configuration for the next boot. This change will only take place after the next boot. The changed configuration will remain effective until it is changed again using this option. The sr_priority for the primary swap for the next boot should always be set to 1. Other priority values are considered invalid. A value of -1 for sr_start implies a presence of a file system on the swap device and swap area to start immediately after that. The length of the device swap to be configured should at least be swchunk kilobytes in size. The length is always rounded down to be a multiple of swchunk. A VxVM or LVM-based logical volume should be created with contiguous layout to be configured as a primary swap device. For LVM-based systems only the logical volumes within the root volume group can be configured as a primary swap device. For a pre-existing directory swap, a value of -1 for sr_min, sr_lim, sr_res, or sr_priority will keep the value unchanged. This can be used to change selective values without affecting others. For example, if priority of a pre-existing directory swap needs to be changed without affecting the values of sr_min, sr_lim, or sr_res, one can specify the new priority value and pass -1 for other arguments. The size for the file system blocks mentioned above is the preferred file system block size. The preferred file system block size can be obtained by the statvfs() call. The SC_REMOVE CommandFor the SC_REMOVE command, arg parameter is a pointer to the swapres structure with the following members: swapctl_flags_t sr_flag char * sr_name int64_t sr_start int64_t sr_length where the fields are as follows:
The sr_name, sr_start, and sr_length should be the same values that were used with the SC_ADD command. The sr_flag indicates that the swap resource that is marked as primary swap for the next boot be removed. This will only work if the primary swap device was configured using the SC_ADD command. Devices that have been configured for swap by methods other than swapctl() can not be altered by the SC_REMOVE command. Swap resources that have been activated for the current boot cannot be removed until the system boot. When using the SC_ADD and SC_REMOVE commands, the calling process fails if the appropriate privileges do not exist for the operation. The SC_LIST CommandFor the SC_LIST command, arg parameter is a pointer to the swaptable structure with following members: int swt_n swapctl_flags_t swt_flag struct swapent swt_ent [] where:
The swapent structure will return the information in the following fields: char *ste_path nt64_t ste_start nt64_t ste_length ev_t ste_dev Before swapctl() is issued, allocate memory to all of the ste_path pointers. Ensure that each of the areas allocated is at least MAXPATHLEN bytes long. MAXPATHLEN is defined in <sys/param.h>. The fields are defined as follows:
The SC_LIST command for now only lists the primary swap device that is configured for next boot. The pstst_getswap() interface has to be used to get the list of all other swap resources. RETURN VALUESOn success, the swapctl() system call returns 0 when used with the SC_ADD or SC_REMOVE commands. For the SC_LIST command, the number of struct swapent entries actually returned indicates success. On error, the swapctl() system call returns a value of -1 and sets errno to indicate the error. ERRORSIf the swapctl() system call fails, errno is set to one of the following:
EXAMPLESThe following example adds, lists and removes a primary swap device for next boot: #include <sys/swap.h> #include <stdio.h> int main() { int rv; swapres_t swp; swaptable_t swt; swapent_t swent; char path[1024] = "/dev/dsk/c4t3d0 "; char ret_path[1024]; bzero(ret_path, 1024); /* add a new primary swap for next boot */ swp.sr_flag = SW_PRIMARY | SW_NEXTBOOT; swp.sr_name = path; swp.sr_start = 0; swp.sr_length = 0; /* 0 len implies, use the entire dev */ swp.sr_priority = 1; rv = swapctl(SC_ADD, (void *)&swp); if (rv) { perror("swapctl/SC_ADD failed"); exit(1); } /* list the swap device configured above */ swent.ste_path = path; swt.swt_n = 1; swt.swt_flags = SW_PRIMARY | SW_NEXTBOOT; swt.swt_ent = &swent; rv = swapctl(SC_LIST, (void *)&swt); if (rv != 1) { /* returns the number of swap devices returned */ printf("swapctl/SC_LIST returned: %d \n", rv); perror("swapctl/SC_LIST failed"); exit(2); } printf("Primary swap for next boot: %s \n", swent.ste_path); /* Remove the above configured primary swap */ swp.sr_flag = SW_PRIMARY | SW_NEXTBOOT; swp.sr_name = path; /* same path as used for SC_ADD */ swp.sr_start = 0; /* same start as used for SC_ADD */ swp.sr_length = 0; /* same length as used for SC_ADD */ swp.sr_priority = 1; rv = swapctl(SC_REMOVE, (void *)&swp); if (rv) { perror("swapctl/SC_REMOVE failed"); exit(3); } return 0; } WARNINGSIf swapctl() is used for configuring primary swap, other methods for configuring primary swap like lvlnboot, vxvmboot, and system configuration files (see lvlnboot(1M), vxvmboot(1M), and system(4)), and PA HP-UX boot loader mechanism will become ineffective. In other words, if a device is configured for primary swap using swapctl(), then other device(s) that are configured for primary swap using the above mentioned methods will not be effective. The lvlnboot, vxvmboot, and system configuration file methods for configuring swap are deprecated and will be obsoleted in future releases. |
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