Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

ubc_release(9) [netbsd man page]

UBC(9)							   BSD Kernel Developer's Manual						    UBC(9)

ubc -- unified buffer cache SYNOPSIS
#include <uvm/uvm.h> void * ubc_alloc(struct uvm_object *uobj, voff_t offset, vsize_t *lenp, int advice, int flags); void ubc_release(void *va, int flags); int ubc_uiomove(struct uvm_object *uobj, struct uio *uio, vsize_t todo, int advice, int flags); void ubc_purge(struct uvm_object *uobj); DESCRIPTION
ubc_alloc() creates a kernel mapping of uobj starting at offset offset. The desired length of the mapping is pointed to by lenp, but the actual mapping may be smaller than this. lenp is updated to contain the actual length mapped. advice is the access pattern hint, which must be one of UVM_ADV_NORMAL No hint UVM_ADV_RANDOM Random access hint UVM_ADV_SEQUENTIAL Sequential access hint (from lower offset to higher offset) The possible flags are UBC_READ Mapping will be accessed for read. UBC_WRITE Mapping will be accessed for write. UBC_FAULTBUSY Fault in window's pages already during mapping operation. Makes sense only for write. Once the mapping is created, it must be accessed only by methods that can handle faults, such as uiomove() or kcopy(). Page faults on the mapping will result in the object's pager method being called to resolve the fault. ubc_release() frees the mapping at va for reuse. The mapping may be cached to speed future accesses to the same region of the object. The flags can be any of UBC_UNMAP Do not cache mapping. ubc_uiomove() allocates an UBC memory window, performs I/O on it and unmaps the window. The advice parameter takes the same values as the respective parameter in ubc_alloc() and the flags parameter takes the same arguments as ubc_alloc() and ubc_release(). Additionally, the flag UBC_PARTIALOK can be provided to indicate that it is acceptable to return if an error occurs mid-transfer. ubc_purge() disassociates all UBC structures from an empty UVM object, specified by uobj. CODE REFERENCES
The ubc subsystem is implemented within the file sys/uvm/uvm_bio.c. SEE ALSO
pmap(9), uiomove(9), uvm(9), vnode(9), vnodeops(9) Chuck Silvers, "UBC: An Efficient Unified I/O and Memory Caching Subsystem for NetBSD", Proceedings of the FREENIX Track: 2000 USENIX Annual Technical Conference, USENIX Association,, 285-290, June 18-23, 2000. HISTORY
UBC first appeared in NetBSD 1.6. AUTHORS
Chuck Silvers <> designed and implemented the UBC part of UVM, which uses UVM pages to cache vnode data rather than the tradi- tional buffer cache buffers. BSD
June 14, 2011 BSD

Check Out this Related Man Page

UVM_MAP(9)						   BSD Kernel Developer's Manual						UVM_MAP(9)

uvm_map -- virtual address space management interface SYNOPSIS
#include <sys/param.h> #include <uvm/uvm.h> int uvm_map(struct vm_map *map, vaddr_t *startp, vsize_t size, struct uvm_object *uobj, voff_t uoffset, vsize_t align, uvm_flag_t flags); void uvm_unmap(struct vm_map *map, vaddr_t start, vaddr_t end); int uvm_map_pageable(struct vm_map *map, vaddr_t start, vaddr_t end, bool new_pageable, int lockflags); bool uvm_map_checkprot(struct vm_map *map, vaddr_t start, vaddr_t end, vm_prot_t protection); int uvm_map_protect(struct vm_map *map, vaddr_t start, vaddr_t end, vm_prot_t new_prot, bool set_max); int uvm_deallocate(struct vm_map *map, vaddr_t start, vsize_t size); struct vmspace * uvmspace_alloc(vaddr_t min, vaddr_t max); void uvmspace_exec(struct lwp *l, vaddr_t start, vaddr_t end); struct vmspace * uvmspace_fork(struct vmspace *vm); void uvmspace_free(struct vmspace *vm); void uvmspace_share(struct proc *p1, struct proc *p2); vaddr_t uvm_uarea_alloc(void); void uvm_uarea_free(vaddr_t uaddr); vaddr_t uvm_uarea_system_alloc(void); void uvm_uarea_system_free(vaddr_t uaddr); DESCRIPTION
The UVM facility for virtual address space management. FUNCTIONS
uvm_map() establishes a valid mapping in map map, which must be unlocked. The new mapping has size size, which must be a multiple of PAGE_SIZE. The uobj and uoffset arguments can have four meanings. When uobj is NULL and uoffset is UVM_UNKNOWN_OFFSET, uvm_map() does not use the machine-dependent PMAP_PREFER function. If uoffset is any other value, it is used as the hint to PMAP_PREFER. When uobj is not NULL and uoffset is UVM_UNKNOWN_OFFSET, uvm_map() finds the offset based upon the virtual address, passed as startp. If uoffset is any other value, then a regular mapping is performed at this offset. The start address of the map will be returned in startp. align specifies alignment of mapping unless UVM_FLAG_FIXED is specified in flags. align must be a power of 2. flags passed to uvm_map() are typically created using the UVM_MAPFLAG(vm_prot_t prot, vm_prot_t maxprot, vm_inherit_t inh, int advice, int flags) macro, which uses the following values. The prot and maxprot can take are: UVM_PROT_NONE No protection bits. UVM_PROT_R Read. UVM_PROT_W Write. UVM_PROT_X Exec. UVM_PROT_MASK Mask to extraction the protection bits. Additionally, the following constants for ORed values are available: UVM_PROT_RW, UVM_PROT_RX, UVM_PROT_WX and UVM_PROT_RWX. The values that inh can take are: UVM_INH_SHARE Share the map. UVM_INH_COPY Copy the map. UVM_INH_NONE No inheritance. UVM_INH_MASK Mark to extract inherit flags. The values that advice can take are: UVM_ADV_NORMAL "Normal" use. UVM_ADV_RANDOM "Random" access likelyhood. UVM_ADV_SEQUENTIAL "Sequential" access likelyhood. UVM_ADV_MASK Mask to extract the advice flags. The values that flags can take are: UVM_FLAG_FIXED Attempt to map on the address specified by startp. Otherwise, it is used just as a hint. UVM_FLAG_OVERLAY Establish overlay. UVM_FLAG_NOMERGE Do not merge map entries, if such merge is possible. UVM_FLAG_COPYONW Use copy-on-write i.e. do not fault in the pages immediately. UVM_FLAG_AMAPPAD User for BSS: alocate larger amap, if extending is likely. UVM_FLAG_TRYLOCK Fail if cannot acquire the lock immediately. UVM_FLAG_NOWAIT Not allowed to sleep. Fail, in such case. UVM_FLAG_QUANTUM Indicates that map entry cannot be split once mapped. UVM_FLAG_WAITVA Sleep until VA space is available, if it is not. UVM_FLAG_VAONLY Unmap only VA space. Used by uvm_unmap(). The UVM_MAPFLAG macro arguments can be combined with an or operator. There are several special purpose macros for checking protection combi- nations, e.g., the UVM_PROT_WX. There are also some additional macros to extract bits from the flags. The UVM_PROTECTION, UVM_INHERIT, UVM_MAXPROTECTION and UVM_ADVICE macros return the protection, inheritance, maximum protection and advice, respectively. uvm_map() returns zero on success or error number otherwise. uvm_unmap() removes a valid mapping, from start to end, in map map, which must be unlocked. uvm_map_pageable() changes the pageability of the pages in the range from start to end in map map to new_pageable. uvm_map_pageable() returns zero on success or error number otherwise. uvm_map_checkprot() checks the protection of the range from start to end in map map against protection. This returns either true or false. uvm_map_protect() changes the protection start to end in map map to new_prot, also setting the maximum protection to the region to new_prot if set_max is true. This function returns a standard UVM return value. uvm_deallocate() deallocates kernel memory in map map from address start to start + size. uvmspace_alloc() allocates and returns a new address space, with ranges from min to max. uvmspace_exec() either reuses the address space of thread l (its process) if there are no other references to it, or creates a new one with uvmspace_alloc(). The range of valid addresses in the address space is reset to start through end. uvmspace_fork() creates and returns a new address space based upon the vm address space, typically used when allocating an address space for a child process. uvmspace_free() lowers the reference count on the address space vm, freeing the data structures if there are no other references. uvmspace_share() causes process p2 to share the address space of p1. uvm_uarea_alloc() allocates memory for a u-area (i.e. kernel stack, PCB, etc) and returns the address. uvm_uarea_free() frees a u-area allocated with uvm_uarea_alloc(). uvm_uarea_system_alloc() and uvm_uarea_system_free() are optimised routines, which are used for kernel threads. SEE ALSO
pmap(9), uvm(9), uvm_km(9), vmem(9) HISTORY
UVM and uvm_map first appeared in NetBSD 1.4. BSD
June 3, 2011 BSD
Man Page