svn commit: r327410 - head/sys/vm
Alan Cox
alc at FreeBSD.org
Sun Dec 31 04:01:48 UTC 2017
Author: alc
Date: Sun Dec 31 04:01:47 2017
New Revision: 327410
URL: https://svnweb.freebsd.org/changeset/base/327410
Log:
Previously, swap_pager_copy() freed swap blocks one at at time, via
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 at rice.edu>
Reviewed by: kib (an earlier version)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D13290
Modified:
head/sys/vm/swap_pager.c
Modified: head/sys/vm/swap_pager.c
==============================================================================
--- head/sys/vm/swap_pager.c Sun Dec 31 03:35:34 2017 (r327409)
+++ head/sys/vm/swap_pager.c Sun Dec 31 04:01:47 2017 (r327410)
@@ -311,8 +311,7 @@ swap_release_by_cred(vm_ooffset_t decr, struct ucred *
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 dst
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 dst
}
/*
- * 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 pin
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 pin
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);
@@ -2040,17 +2030,13 @@ swp_pager_meta_ctl(vm_object_t object, vm_pindex_t pin
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,
rounddown(pindex, SWAP_META_PAGES));
uma_zfree(swblk_zone, sb);
}
- }
- if ((flags & SWM_FREE) != 0) {
- swp_pager_freeswapspace(r1, 1);
- r1 = SWAPBLK_NONE;
}
return (r1);
}
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