mirror of
https://github.com/freebsd/freebsd-src
synced 2024-10-15 12:54:27 +00:00
Update some comments in swap_pager.c.
Reviewed and most wording by: alc MFC after: 1 week Approved by: re (bz)
This commit is contained in:
parent
462d5251d7
commit
15523cf799
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=225089
|
@ -114,9 +114,9 @@ __FBSDID("$FreeBSD$");
|
|||
#include <geom/geom.h>
|
||||
|
||||
/*
|
||||
* SWB_NPAGES must be a power of 2. It may be set to 1, 2, 4, 8, or 16
|
||||
* pages per allocation. We recommend you stick with the default of 8.
|
||||
* The 16-page limit is due to the radix code (kern/subr_blist.c).
|
||||
* SWB_NPAGES must be a power of 2. It may be set to 1, 2, 4, 8, 16
|
||||
* or 32 pages per allocation.
|
||||
* The 32-page limit is due to the radix code (kern/subr_blist.c).
|
||||
*/
|
||||
#ifndef MAX_PAGEOUT_CLUSTER
|
||||
#define MAX_PAGEOUT_CLUSTER 16
|
||||
|
@ -127,14 +127,11 @@ __FBSDID("$FreeBSD$");
|
|||
#endif
|
||||
|
||||
/*
|
||||
* Piecemeal swap metadata structure. Swap is stored in a radix tree.
|
||||
*
|
||||
* If SWB_NPAGES is 8 and sizeof(char *) == sizeof(daddr_t), our radix
|
||||
* is basically 8. Assuming PAGE_SIZE == 4096, one tree level represents
|
||||
* 32K worth of data, two levels represent 256K, three levels represent
|
||||
* 2 MBytes. This is acceptable.
|
||||
*
|
||||
* Overall memory utilization is about the same as the old swap structure.
|
||||
* The swblock structure maps an object and a small, fixed-size range
|
||||
* of page indices to disk addresses within a swap area.
|
||||
* The collection of these mappings is implemented as a hash table.
|
||||
* Unused disk addresses within a swap area are allocated and managed
|
||||
* using a blist.
|
||||
*/
|
||||
#define SWCORRECT(n) (sizeof(void *) * (n) / sizeof(daddr_t))
|
||||
#define SWAP_META_PAGES (SWB_NPAGES * 2)
|
||||
|
@ -662,9 +659,7 @@ swap_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
|
|||
* routine is typically called only when the entire object is
|
||||
* about to be destroyed.
|
||||
*
|
||||
* This routine may block, but no longer does.
|
||||
*
|
||||
* The object must be locked or unreferenceable.
|
||||
* The object must be locked.
|
||||
*/
|
||||
static void
|
||||
swap_pager_dealloc(vm_object_t object)
|
||||
|
@ -706,7 +701,7 @@ swap_pager_dealloc(vm_object_t object)
|
|||
* Also has the side effect of advising that somebody made a mistake
|
||||
* when they configured swap and didn't configure enough.
|
||||
*
|
||||
* This routine may not block
|
||||
* This routine may not sleep.
|
||||
*
|
||||
* We allocate in round-robin fashion from the configured devices.
|
||||
*/
|
||||
|
@ -776,10 +771,7 @@ swp_pager_strategy(struct buf *bp)
|
|||
*
|
||||
* This routine returns the specified swap blocks back to the bitmap.
|
||||
*
|
||||
* Note: This routine may not block (it could in the old swap code),
|
||||
* and through the use of the new blist routines it does not block.
|
||||
*
|
||||
* This routine may not block
|
||||
* This routine may not sleep.
|
||||
*/
|
||||
static void
|
||||
swp_pager_freeswapspace(daddr_t blk, int npages)
|
||||
|
@ -875,21 +867,16 @@ swap_pager_reserve(vm_object_t object, vm_pindex_t start, vm_size_t size)
|
|||
* cases where both the source and destination have a valid swapblk,
|
||||
* we keep the destination's.
|
||||
*
|
||||
* This routine is allowed to block. It may block allocating metadata
|
||||
* This routine is allowed to sleep. It may sleep allocating metadata
|
||||
* indirectly through swp_pager_meta_build() or if paging is still in
|
||||
* progress on the source.
|
||||
*
|
||||
* XXX vm_page_collapse() kinda expects us not to block because we
|
||||
* supposedly do not need to allocate memory, but for the moment we
|
||||
* *may* have to get a little memory from the zone allocator, but
|
||||
* it is taken from the interrupt memory. We should be ok.
|
||||
*
|
||||
* The source object contains no vm_page_t's (which is just as well)
|
||||
*
|
||||
* The source object is of type OBJT_SWAP.
|
||||
*
|
||||
* The source and destination objects must be locked or
|
||||
* inaccessible (XXX are they ?)
|
||||
* The source and destination objects must be locked.
|
||||
* Both object locks may temporarily be released.
|
||||
*/
|
||||
void
|
||||
swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject,
|
||||
|
@ -1066,7 +1053,7 @@ swap_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before, int *aft
|
|||
* does NOT change the m->dirty status of the page. Also: MADV_FREE
|
||||
* depends on it.
|
||||
*
|
||||
* This routine may not block
|
||||
* This routine may not sleep.
|
||||
*/
|
||||
static void
|
||||
swap_pager_unswapped(vm_page_t m)
|
||||
|
@ -1472,7 +1459,7 @@ swap_pager_putpages(vm_object_t object, vm_page_t *m, int count,
|
|||
* operations, we vm_page_t->busy'd unbusy all pages ( we can do this
|
||||
* because we marked them all VM_PAGER_PEND on return from putpages ).
|
||||
*
|
||||
* This routine may not block.
|
||||
* This routine may not sleep.
|
||||
*/
|
||||
static void
|
||||
swp_pager_async_iodone(struct buf *bp)
|
||||
|
@ -1657,7 +1644,7 @@ swp_pager_async_iodone(struct buf *bp)
|
|||
* Return 1 if at least one page in the given object is paged
|
||||
* out to the given swap device.
|
||||
*
|
||||
* This routine may not block.
|
||||
* This routine may not sleep.
|
||||
*/
|
||||
int
|
||||
swap_pager_isswapped(vm_object_t object, struct swdevt *sp)
|
||||
|
|
Loading…
Reference in a new issue