d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Previously, swap_pager_copy() freed swap blocks one at at time, via

Browse Source 
swp_pager_meta_ctl(), with no opportunity to recognize freeing of
consecutive blocks and free fewer block ranges.  To open that opportunity,
this change removes the SWM_FREE option from swp_pager_meta_ctl(), and
compels the caller to do the freeing when a valid block address is returned.
In swap_pager_copy(), these frees are aggregated, so that a sequence of them
can be done at one time.

The only other caller to swp_pager_meta_ctl() that passed SWM_FREE,
swp_pager_unswapped(), is also modified to handle its single free
explicitly.

Submitted by:	Doug Moore <dougm@rice.edu>
Reviewed by:	kib (an earlier version)
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D13290
This commit is contained in:
Alan Cox 2017-12-31 04:01:47 +00:00
parent 0879ca728a
commit 4abca9bb05
1 changed files with 36 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

86
sys/vm/swap_pager.c
View File

@ -311,8 +311,7 @@ swap_release_by_cred(vm_ooffset_t decr, struct ucred *cred)
racct_sub_cred(cred, RACCT_SWAP, decr);
}
#define SWM_FREE 0x02 /* free, period */
#define SWM_POP 0x04 /* pop out */
#define SWM_POP 0x01 /* pop out */
static int swap_pager_full = 2; /* swap space exhaustion (task killing) */
static int swap_pager_almost_full = 1; /* swap space exhaustion (w/hysteresis)*/
@ -911,6 +910,7 @@ swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject,
vm_pindex_t offset, int destroysource)
{
vm_pindex_t i;
daddr_t dstaddr, first_free, num_free, srcaddr;
VM_OBJECT_ASSERT_WLOCKED(srcobject);
VM_OBJECT_ASSERT_WLOCKED(dstobject);
@ -935,53 +935,44 @@ swap_pager_copy(vm_object_t srcobject, vm_object_t dstobject,
}
/*
* transfer source to destination.
* Transfer source to destination.
*/
first_free = SWAPBLK_NONE;
num_free = 0;
for (i = 0; i < dstobject->size; ++i) {
daddr_t dstaddr;
/*
* Locate (without changing) the swapblk on the destination,
* unless it is invalid in which case free it silently, or
* if the destination is a resident page, in which case the
* source is thrown away.
*/
srcaddr = swp_pager_meta_ctl(srcobject, i + offset, SWM_POP);
if (srcaddr == SWAPBLK_NONE)
continue;
dstaddr = swp_pager_meta_ctl(dstobject, i, 0);
if (dstaddr == SWAPBLK_NONE) {
/*
* Destination has no swapblk and is not resident,
* copy source.
*
* swp_pager_meta_build() can sleep.
*/
daddr_t srcaddr;
srcaddr = swp_pager_meta_ctl(
srcobject,
i + offset,
SWM_POP
);
if (srcaddr != SWAPBLK_NONE) {
/*
* swp_pager_meta_build() can sleep.
*/
vm_object_pip_add(srcobject, 1);
VM_OBJECT_WUNLOCK(srcobject);
vm_object_pip_add(dstobject, 1);
swp_pager_meta_build(dstobject, i, srcaddr);
vm_object_pip_wakeup(dstobject);
VM_OBJECT_WLOCK(srcobject);
vm_object_pip_wakeup(srcobject);
}
vm_object_pip_add(srcobject, 1);
VM_OBJECT_WUNLOCK(srcobject);
vm_object_pip_add(dstobject, 1);
swp_pager_meta_build(dstobject, i, srcaddr);
vm_object_pip_wakeup(dstobject);
VM_OBJECT_WLOCK(srcobject);
vm_object_pip_wakeup(srcobject);
} else {
/*
* Destination has valid swapblk or it is represented
* by a resident page. We destroy the sourceblock.
*/
swp_pager_meta_ctl(srcobject, i + offset, SWM_FREE);
if (first_free + num_free == srcaddr)
num_free++;
else {
swp_pager_freeswapspace(first_free, num_free);
first_free = srcaddr;
num_free = 1;
}
}
}
swp_pager_freeswapspace(first_free, num_free);
/*
* Free left over swap blocks in source.
@ -1082,8 +1073,11 @@ swap_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
static void
swap_pager_unswapped(vm_page_t m)
{
daddr_t srcaddr;
swp_pager_meta_ctl(m->object, m->pindex, SWM_FREE);
srcaddr = swp_pager_meta_ctl(m->object, m->pindex, SWM_POP);
if (srcaddr != SWAPBLK_NONE)
swp_pager_freeswapspace(srcaddr, 1);
}
/*
@ -1999,21 +1993,17 @@ swp_pager_meta_free_all(vm_object_t object)
}
/*
* SWP_PAGER_METACTL() - misc control of swap and vm_page_t meta data.
* SWP_PAGER_METACTL() - misc control of swap meta data.
*
* This routine is capable of looking up, popping, or freeing
* swapblk assignments in the swap meta data or in the vm_page_t.
* The routine typically returns the swapblk being looked-up, or popped,
* or SWAPBLK_NONE if the block was freed, or SWAPBLK_NONE if the block
* was invalid. This routine will automatically free any invalid
* meta-data swapblks.
* This routine is capable of looking up, or removing swapblk
* assignments in the swap meta data. It returns the swapblk being
* looked-up, popped, or SWAPBLK_NONE if the block was invalid.
*
* When acting on a busy resident page and paging is in progress, we
* have to wait until paging is complete but otherwise can act on the
* busy page.
*
* SWM_FREE remove and free swap block from metadata
* SWM_POP remove from meta data but do not free.. pop it out
* SWM_POP remove from meta data but do not free it
*/
static daddr_t
swp_pager_meta_ctl(vm_object_t object, vm_pindex_t pindex, int flags)
@ -2021,7 +2011,7 @@ swp_pager_meta_ctl(vm_object_t object, vm_pindex_t pindex, int flags)
struct swblk *sb;
daddr_t r1;
if ((flags & (SWM_FREE | SWM_POP)) != 0)
if ((flags & SWM_POP) != 0)
VM_OBJECT_ASSERT_WLOCKED(object);
else
VM_OBJECT_ASSERT_LOCKED(object);
@ -2040,7 +2030,7 @@ swp_pager_meta_ctl(vm_object_t object, vm_pindex_t pindex, int flags)
r1 = sb->d[pindex % SWAP_META_PAGES];
if (r1 == SWAPBLK_NONE)
return (SWAPBLK_NONE);
if ((flags & (SWM_FREE | SWM_POP)) != 0) {
if ((flags & SWM_POP) != 0) {
sb->d[pindex % SWAP_META_PAGES] = SWAPBLK_NONE;
if (swp_pager_swblk_empty(sb, 0, SWAP_META_PAGES)) {
SWAP_PCTRIE_REMOVE(&object->un_pager.swp.swp_blks,
@ -2048,10 +2038,6 @@ swp_pager_meta_ctl(vm_object_t object, vm_pindex_t pindex, int flags)
uma_zfree(swblk_zone, sb);
}
}
if ((flags & SWM_FREE) != 0) {
swp_pager_freeswapspace(r1, 1);
r1 = SWAPBLK_NONE;
}
return (r1);
}