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Subject[PATCH 6/9] VMware balloon: Do not limit the amount of frees and allocations in non-sleep mode.
Date
Before this patch the slow memory transfer would cause the destination VM to
have internal swapping until all memory is transferred. Now the memory is
transferred fast enough so that the destination VM does not swap. The balloon
loop already yields to the rest of the system, hence the balloon thread
should not monopolize a cpu.

Testing Done: quickly ballooned a lot of pages while wathing if there are any
perceived hickups (periods of non-responsiveness) in the execution of the
linux VM. No such hickups were seen.

Signed-off-by: Xavier Deguillard <xdeguillard@vmware.com>
---
drivers/misc/vmw_balloon.c | 66 +++++++++++-----------------------------------
1 file changed, 15 insertions(+), 51 deletions(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 6eaf7f7..a5e1980 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -46,7 +46,7 @@

MODULE_AUTHOR("VMware, Inc.");
MODULE_DESCRIPTION("VMware Memory Control (Balloon) Driver");
-MODULE_VERSION("1.3.3.0-k");
+MODULE_VERSION("1.3.4.0-k");
MODULE_ALIAS("dmi:*:svnVMware*:*");
MODULE_ALIAS("vmware_vmmemctl");
MODULE_LICENSE("GPL");
@@ -57,12 +57,6 @@ MODULE_LICENSE("GPL");
*/

/*
- * Rate of allocating memory when there is no memory pressure
- * (driver performs non-sleeping allocations).
- */
-#define VMW_BALLOON_NOSLEEP_ALLOC_MAX 16384U
-
-/*
* Rates of memory allocaton when guest experiences memory pressure
* (driver performs sleeping allocations).
*/
@@ -71,13 +65,6 @@ MODULE_LICENSE("GPL");
#define VMW_BALLOON_RATE_ALLOC_INC 16U

/*
- * Rates for releasing pages while deflating balloon.
- */
-#define VMW_BALLOON_RATE_FREE_MIN 512U
-#define VMW_BALLOON_RATE_FREE_MAX 16384U
-#define VMW_BALLOON_RATE_FREE_INC 16U
-
-/*
* When guest is under memory pressure, use a reduced page allocation
* rate for next several cycles.
*/
@@ -99,9 +86,6 @@ MODULE_LICENSE("GPL");
*/
#define VMW_PAGE_ALLOC_CANSLEEP (GFP_HIGHUSER)

-/* Maximum number of page allocations without yielding processor */
-#define VMW_BALLOON_YIELD_THRESHOLD 1024
-
/* Maximum number of refused pages we accumulate during inflation cycle */
#define VMW_BALLOON_MAX_REFUSED 16

@@ -278,7 +262,6 @@ struct vmballoon {

/* adjustment rates (pages per second) */
unsigned int rate_alloc;
- unsigned int rate_free;

/* slowdown page allocations for next few cycles */
unsigned int slow_allocation_cycles;
@@ -502,18 +485,13 @@ static bool vmballoon_send_batched_unlock(struct vmballoon *b,
static void vmballoon_pop(struct vmballoon *b)
{
struct page *page, *next;
- unsigned int count = 0;

list_for_each_entry_safe(page, next, &b->pages, lru) {
list_del(&page->lru);
__free_page(page);
STATS_INC(b->stats.free);
b->size--;
-
- if (++count >= b->rate_free) {
- count = 0;
- cond_resched();
- }
+ cond_resched();
}

if ((b->capabilities & VMW_BALLOON_BATCHED_CMDS) != 0) {
@@ -742,13 +720,13 @@ static void vmballoon_inflate(struct vmballoon *b)
* Start with no sleep allocation rate which may be higher
* than sleeping allocation rate.
*/
- rate = b->slow_allocation_cycles ?
- b->rate_alloc : VMW_BALLOON_NOSLEEP_ALLOC_MAX;
+ rate = b->slow_allocation_cycles ? b->rate_alloc : -1;

pr_debug("%s - goal: %d, no-sleep rate: %d, sleep rate: %d\n",
__func__, b->target - b->size, rate, b->rate_alloc);

- while (b->size < b->target && num_pages < b->target - b->size) {
+ while (!b->reset_required &&
+ b->size < b->target && num_pages < b->target - b->size) {
struct page *page;

if (flags == VMW_PAGE_ALLOC_NOSLEEP)
@@ -798,12 +776,9 @@ static void vmballoon_inflate(struct vmballoon *b)
break;
}

- if (++allocations > VMW_BALLOON_YIELD_THRESHOLD) {
- cond_resched();
- allocations = 0;
- }
+ cond_resched();

- if (allocations >= rate) {
+ if (rate != -1 && allocations >= rate) {
/* We allocated enough pages, let's take a break. */
break;
}
@@ -837,36 +812,29 @@ static void vmballoon_deflate(struct vmballoon *b)
unsigned int num_pages = 0;
int error;

- pr_debug("%s - size: %d, target %d, rate: %d\n", __func__, b->size,
- b->target, b->rate_free);
+ pr_debug("%s - size: %d, target %d\n", __func__, b->size, b->target);

/* free pages to reach target */
list_for_each_entry_safe(page, next, &b->pages, lru) {
list_del(&page->lru);
b->ops->add_page(b, num_pages++, page);

+
if (num_pages == b->batch_max_pages) {
error = b->ops->unlock(b, num_pages, &b->target);
num_pages = 0;
- if (error) {
- /* quickly decrease rate in case of error */
- b->rate_free = max(b->rate_free / 2,
- VMW_BALLOON_RATE_FREE_MIN);
+ if (error)
return;
- }
}

- if (++i >= b->size - b->target)
+ if (b->reset_required || ++i >= b->size - b->target)
break;
+
+ cond_resched();
}

if (num_pages > 0)
b->ops->unlock(b, num_pages, &b->target);
-
- /* slowly increase rate if there were no errors */
- if (error == 0)
- b->rate_free = min(b->rate_free + VMW_BALLOON_RATE_FREE_INC,
- VMW_BALLOON_RATE_FREE_MAX);
}

static const struct vmballoon_ops vmballoon_basic_ops = {
@@ -992,11 +960,8 @@ static int vmballoon_debug_show(struct seq_file *f, void *offset)

/* format rate info */
seq_printf(f,
- "rateNoSleepAlloc: %8d pages/sec\n"
- "rateSleepAlloc: %8d pages/sec\n"
- "rateFree: %8d pages/sec\n",
- VMW_BALLOON_NOSLEEP_ALLOC_MAX,
- b->rate_alloc, b->rate_free);
+ "rateSleepAlloc: %8d pages/sec\n",
+ b->rate_alloc);

seq_printf(f,
"\n"
@@ -1087,7 +1052,6 @@ static int __init vmballoon_init(void)

/* initialize rates */
balloon.rate_alloc = VMW_BALLOON_RATE_ALLOC_MAX;
- balloon.rate_free = VMW_BALLOON_RATE_FREE_MAX;

INIT_DELAYED_WORK(&balloon.dwork, vmballoon_work);

--
1.9.3


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