[PATCH v4 3/9] VMware balloon: add batching to the vmw_balloon.

Philip P. Moltmann
2015-08-06T20:34:48Z

From: Xavier Deguillard <xdeguillard@vmware.com>

Introduce a new capability to the driver that allow sending 512 pages in
one hypervisor call. This reduce the cost of the driver when reclaiming
memory.

Signed-off-by: Xavier Deguillard <xdeguillard@vmware.com>
Acked-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Philip P. Moltmann <moltmann@vmware.com>
---
drivers/misc/vmw_balloon.c | 406 +++++++++++++++++++++++++++++++++++++++------
1 file changed, 353 insertions(+), 53 deletions(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index ffb5634..64f275e 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -1,7 +1,7 @@
/*
* VMware Balloon driver.
*
- * Copyright (C) 2000-2010, VMware, Inc. All Rights Reserved.
+ * Copyright (C) 2000-2013, VMware, Inc. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
@@ -37,6 +37,7 @@
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
+#include <linux/vmalloc.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/workqueue.h>
@@ -46,7 +47,7 @@

MODULE_AUTHOR("VMware, Inc.");
MODULE_DESCRIPTION("VMware Memory Control (Balloon) Driver");
-MODULE_VERSION("1.3.0.0-k");
+MODULE_VERSION("1.3.1.0-k");
MODULE_ALIAS("dmi:*:svnVMware*:*");
MODULE_ALIAS("vmware_vmmemctl");
MODULE_LICENSE("GPL");
@@ -120,13 +121,26 @@ enum vmwballoon_capabilities {
VMW_BALLOON_BATCHED_CMDS = (1 << 2)
};

-#define VMW_BALLOON_CAPABILITIES (VMW_BALLOON_BASIC_CMDS)
+#define VMW_BALLOON_CAPABILITIES (VMW_BALLOON_BASIC_CMDS \
+ | VMW_BALLOON_BATCHED_CMDS)

+/*
+ * Backdoor commands availability:
+ *
+ * START, GET_TARGET and GUEST_ID are always available,
+ *
+ * VMW_BALLOON_BASIC_CMDS:
+ * LOCK and UNLOCK commands,
+ * VMW_BALLOON_BATCHED_CMDS:
+ * BATCHED_LOCK and BATCHED_UNLOCK commands.
+ */
#define VMW_BALLOON_CMD_START 0
#define VMW_BALLOON_CMD_GET_TARGET 1
#define VMW_BALLOON_CMD_LOCK 2
#define VMW_BALLOON_CMD_UNLOCK 3
#define VMW_BALLOON_CMD_GUEST_ID 4
+#define VMW_BALLOON_CMD_BATCHED_LOCK 6
+#define VMW_BALLOON_CMD_BATCHED_UNLOCK 7

/* error codes */
#define VMW_BALLOON_SUCCESS 0
@@ -142,18 +156,63 @@ enum vmwballoon_capabilities {

#define VMW_BALLOON_SUCCESS_WITH_CAPABILITIES (0x03000000)

-#define VMWARE_BALLOON_CMD(cmd, data, result) \
+/* Batch page description */
+
+/*
+ * Layout of a page in the batch page:
+ *
+ * +-------------+----------+--------+
+ * | | | |
+ * | Page number | Reserved | Status |
+ * | | | |
+ * +-------------+----------+--------+
+ * 64 PAGE_SHIFT 6 0
+ *
+ * For now only 4K pages are supported, but we can easily support large pages
+ * by using bits in the reserved field.
+ *
+ * The reserved field should be set to 0.
+ */
+#define VMW_BALLOON_BATCH_MAX_PAGES (PAGE_SIZE / sizeof(u64))
+#define VMW_BALLOON_BATCH_STATUS_MASK ((1UL << 5) - 1)
+#define VMW_BALLOON_BATCH_PAGE_MASK (~((1UL << PAGE_SHIFT) - 1))
+
+struct vmballoon_batch_page {
+ u64 pages[VMW_BALLOON_BATCH_MAX_PAGES];
+};
+
+static u64 vmballoon_batch_get_pa(struct vmballoon_batch_page *batch, int idx)
+{
+ return batch->pages[idx] & VMW_BALLOON_BATCH_PAGE_MASK;
+}
+
+static int vmballoon_batch_get_status(struct vmballoon_batch_page *batch,
+ int idx)
+{
+ return (int)(batch->pages[idx] & VMW_BALLOON_BATCH_STATUS_MASK);
+}
+
+static void vmballoon_batch_set_pa(struct vmballoon_batch_page *batch, int idx,
+ u64 pa)
+{
+ batch->pages[idx] = pa;
+}
+
+
+#define VMWARE_BALLOON_CMD(cmd, arg1, arg2, result) \
({ \
- unsigned long __status, __dummy1, __dummy2; \
+ unsigned long __status, __dummy1, __dummy2, __dummy3; \
__asm__ __volatile__ ("inl %%dx" : \
"=a"(__status), \
"=c"(__dummy1), \
"=d"(__dummy2), \
- "=b"(result) : \
+ "=b"(result), \
+ "=S" (__dummy3) : \
"0"(VMW_BALLOON_HV_MAGIC), \
"1"(VMW_BALLOON_CMD_##cmd), \
"2"(VMW_BALLOON_HV_PORT), \
- "3"(data) : \
+ "3"(arg1), \
+ "4" (arg2) : \
"memory"); \
if (VMW_BALLOON_CMD_##cmd == VMW_BALLOON_CMD_START) \
result = __dummy1; \
@@ -192,6 +251,14 @@ struct vmballoon_stats {
#define STATS_INC(stat)
#endif

+struct vmballoon;
+
+struct vmballoon_ops {
+ void (*add_page)(struct vmballoon *b, int idx, struct page *p);
+ int (*lock)(struct vmballoon *b, unsigned int num_pages);
+ int (*unlock)(struct vmballoon *b, unsigned int num_pages);
+};
+
struct vmballoon {

/* list of reserved physical pages */
@@ -215,6 +282,14 @@ struct vmballoon {
/* slowdown page allocations for next few cycles */
unsigned int slow_allocation_cycles;

+ unsigned long capabilities;
+
+ struct vmballoon_batch_page *batch_page;
+ unsigned int batch_max_pages;
+ struct page *page;
+
+ const struct vmballoon_ops *ops;
+
#ifdef CONFIG_DEBUG_FS
/* statistics */
struct vmballoon_stats stats;
@@ -234,16 +309,22 @@ static struct vmballoon balloon;
* Send "start" command to the host, communicating supported version
* of the protocol.
*/
-static bool vmballoon_send_start(struct vmballoon *b)
+static bool vmballoon_send_start(struct vmballoon *b, unsigned long req_caps)
{
- unsigned long status, capabilities;
+ unsigned long status, capabilities, dummy = 0;

STATS_INC(b->stats.start);

- status = VMWARE_BALLOON_CMD(START, VMW_BALLOON_CAPABILITIES,
- capabilities);
- if (status == VMW_BALLOON_SUCCESS)
+ status = VMWARE_BALLOON_CMD(START, req_caps, dummy, capabilities);
+
+ switch (status) {
+ case VMW_BALLOON_SUCCESS_WITH_CAPABILITIES:
+ b->capabilities = capabilities;
+ return true;
+ case VMW_BALLOON_SUCCESS:
+ b->capabilities = VMW_BALLOON_BASIC_CMDS;
return true;
+ }

pr_debug("%s - failed, hv returns %ld\n", __func__, status);
STATS_INC(b->stats.start_fail);
@@ -273,9 +354,10 @@ static bool vmballoon_check_status(struct vmballoon *b, unsigned long status)
*/
static bool vmballoon_send_guest_id(struct vmballoon *b)
{
- unsigned long status, dummy;
+ unsigned long status, dummy = 0;

- status = VMWARE_BALLOON_CMD(GUEST_ID, VMW_BALLOON_GUEST_ID, dummy);
+ status = VMWARE_BALLOON_CMD(GUEST_ID, VMW_BALLOON_GUEST_ID, dummy,
+ dummy);

STATS_INC(b->stats.guest_type);

@@ -295,6 +377,7 @@ static bool vmballoon_send_get_target(struct vmballoon *b, u32 *new_target)
unsigned long status;
unsigned long target;
unsigned long limit;
+ unsigned long dummy = 0;
u32 limit32;

/*
@@ -313,7 +396,7 @@ static bool vmballoon_send_get_target(struct vmballoon *b, u32 *new_target)
/* update stats */
STATS_INC(b->stats.target);

- status = VMWARE_BALLOON_CMD(GET_TARGET, limit, target);
+ status = VMWARE_BALLOON_CMD(GET_TARGET, limit, dummy, target);
if (vmballoon_check_status(b, status)) {
*new_target = target;
return true;
@@ -332,7 +415,7 @@ static bool vmballoon_send_get_target(struct vmballoon *b, u32 *new_target)
static int vmballoon_send_lock_page(struct vmballoon *b, unsigned long pfn,
unsigned int *hv_status)
{
- unsigned long status, dummy;
+ unsigned long status, dummy = 0;
u32 pfn32;

pfn32 = (u32)pfn;
@@ -341,7 +424,7 @@ static int vmballoon_send_lock_page(struct vmballoon *b, unsigned long pfn,

STATS_INC(b->stats.lock);

- *hv_status = status = VMWARE_BALLOON_CMD(LOCK, pfn, dummy);
+ *hv_status = status = VMWARE_BALLOON_CMD(LOCK, pfn, dummy, dummy);
if (vmballoon_check_status(b, status))
return 0;

@@ -350,13 +433,30 @@ static int vmballoon_send_lock_page(struct vmballoon *b, unsigned long pfn,
return 1;
}

+static int vmballoon_send_batched_lock(struct vmballoon *b,
+ unsigned int num_pages)
+{
+ unsigned long status, dummy;
+ unsigned long pfn = page_to_pfn(b->page);
+
+ STATS_INC(b->stats.lock);
+
+ status = VMWARE_BALLOON_CMD(BATCHED_LOCK, pfn, num_pages, dummy);
+ if (vmballoon_check_status(b, status))
+ return 0;
+
+ pr_debug("%s - batch ppn %lx, hv returns %ld\n", __func__, pfn, status);
+ STATS_INC(b->stats.lock_fail);
+ return 1;
+}
+
/*
* Notify the host that guest intends to release given page back into
* the pool of available (to the guest) pages.
*/
static bool vmballoon_send_unlock_page(struct vmballoon *b, unsigned long pfn)
{
- unsigned long status, dummy;
+ unsigned long status, dummy = 0;
u32 pfn32;

pfn32 = (u32)pfn;
@@ -365,7 +465,7 @@ static bool vmballoon_send_unlock_page(struct vmballoon *b, unsigned long pfn)

STATS_INC(b->stats.unlock);

- status = VMWARE_BALLOON_CMD(UNLOCK, pfn, dummy);
+ status = VMWARE_BALLOON_CMD(UNLOCK, pfn, dummy, dummy);
if (vmballoon_check_status(b, status))
return true;

@@ -374,6 +474,23 @@ static bool vmballoon_send_unlock_page(struct vmballoon *b, unsigned long pfn)
return false;
}

+static bool vmballoon_send_batched_unlock(struct vmballoon *b,
+ unsigned int num_pages)
+{
+ unsigned long status, dummy;
+ unsigned long pfn = page_to_pfn(b->page);
+
+ STATS_INC(b->stats.unlock);
+
+ status = VMWARE_BALLOON_CMD(BATCHED_UNLOCK, pfn, num_pages, dummy);
+ if (vmballoon_check_status(b, status))
+ return true;
+
+ pr_debug("%s - batch ppn %lx, hv returns %ld\n", __func__, pfn, status);
+ STATS_INC(b->stats.unlock_fail);
+ return false;
+}
+
/*
* Quickly release all pages allocated for the balloon. This function is
* called when host decides to "reset" balloon for one reason or another.
@@ -396,22 +513,13 @@ static void vmballoon_pop(struct vmballoon *b)
cond_resched();
}
}
-}

-/*
- * Perform standard reset sequence by popping the balloon (in case it
- * is not empty) and then restarting protocol. This operation normally
- * happens when host responds with VMW_BALLOON_ERROR_RESET to a command.
- */
-static void vmballoon_reset(struct vmballoon *b)
-{
- /* free all pages, skipping monitor unlock */
- vmballoon_pop(b);
+ if ((b->capabilities & VMW_BALLOON_BATCHED_CMDS) != 0) {
+ if (b->batch_page)
+ vunmap(b->batch_page);

- if (vmballoon_send_start(b)) {
- b->reset_required = false;
- if (!vmballoon_send_guest_id(b))
- pr_err("failed to send guest ID to the host\n");
+ if (b->page)
+ __free_page(b->page);
}
}

@@ -420,9 +528,10 @@ static void vmballoon_reset(struct vmballoon *b)
* refuse list, those refused page are then released at the end of the
* inflation cycle.
*/
-static int vmballoon_lock_page(struct vmballoon *b, struct page *page)
+static int vmballoon_lock_page(struct vmballoon *b, unsigned int num_pages)
{
int locked, hv_status;
+ struct page *page = b->page;

locked = vmballoon_send_lock_page(b, page_to_pfn(page), &hv_status);
if (locked > 0) {
@@ -457,17 +566,68 @@ static int vmballoon_lock_page(struct vmballoon *b, struct page *page)
return 0;
}

+static int vmballoon_lock_batched_page(struct vmballoon *b,
+ unsigned int num_pages)
+{
+ int locked, i;
+
+ locked = vmballoon_send_batched_lock(b, num_pages);
+ if (locked > 0) {
+ for (i = 0; i < num_pages; i++) {
+ u64 pa = vmballoon_batch_get_pa(b->batch_page, i);
+ struct page *p = pfn_to_page(pa >> PAGE_SHIFT);
+
+ __free_page(p);
+ }
+
+ return -EIO;
+ }
+
+ for (i = 0; i < num_pages; i++) {
+ u64 pa = vmballoon_batch_get_pa(b->batch_page, i);
+ struct page *p = pfn_to_page(pa >> PAGE_SHIFT);
+
+ locked = vmballoon_batch_get_status(b->batch_page, i);
+
+ switch (locked) {
+ case VMW_BALLOON_SUCCESS:
+ list_add(&p->lru, &b->pages);
+ b->size++;
+ break;
+ case VMW_BALLOON_ERROR_PPN_PINNED:
+ case VMW_BALLOON_ERROR_PPN_INVALID:
+ if (b->n_refused_pages < VMW_BALLOON_MAX_REFUSED) {
+ list_add(&p->lru, &b->refused_pages);
+ b->n_refused_pages++;
+ break;
+ }
+ /* Fallthrough */
+ case VMW_BALLOON_ERROR_RESET:
+ case VMW_BALLOON_ERROR_PPN_NOTNEEDED:
+ __free_page(p);
+ break;
+ default:
+ /* This should never happen */
+ WARN_ON_ONCE(true);
+ }
+ }
+
+ return 0;
+}
+
/*
* Release the page allocated for the balloon. Note that we first notify
* the host so it can make sure the page will be available for the guest
* to use, if needed.
*/
-static int vmballoon_release_page(struct vmballoon *b, struct page *page)
+static int vmballoon_unlock_page(struct vmballoon *b, unsigned int num_pages)
{
- if (!vmballoon_send_unlock_page(b, page_to_pfn(page)))
- return -EIO;
+ struct page *page = b->page;

- list_del(&page->lru);
+ if (!vmballoon_send_unlock_page(b, page_to_pfn(page))) {
+ list_add(&page->lru, &b->pages);
+ return -EIO;
+ }

/* deallocate page */
__free_page(page);
@@ -479,6 +639,41 @@ static int vmballoon_release_page(struct vmballoon *b, struct page *page)
return 0;
}

+static int vmballoon_unlock_batched_page(struct vmballoon *b,
+ unsigned int num_pages)
+{
+ int locked, i, ret = 0;
+ bool hv_success;
+
+ hv_success = vmballoon_send_batched_unlock(b, num_pages);
+ if (!hv_success)
+ ret = -EIO;
+
+ for (i = 0; i < num_pages; i++) {
+ u64 pa = vmballoon_batch_get_pa(b->batch_page, i);
+ struct page *p = pfn_to_page(pa >> PAGE_SHIFT);
+
+ locked = vmballoon_batch_get_status(b->batch_page, i);
+ if (!hv_success || locked != VMW_BALLOON_SUCCESS) {
+ /*
+ * That page wasn't successfully unlocked by the
+ * hypervisor, re-add it to the list of pages owned by
+ * the balloon driver.
+ */
+ list_add(&p->lru, &b->pages);
+ } else {
+ /* deallocate page */
+ __free_page(p);
+ STATS_INC(b->stats.free);
+
+ /* update balloon size */
+ b->size--;
+ }
+ }
+
+ return ret;
+}
+
/*
* Release pages that were allocated while attempting to inflate the
* balloon but were refused by the host for one reason or another.
@@ -496,6 +691,18 @@ static void vmballoon_release_refused_pages(struct vmballoon *b)
b->n_refused_pages = 0;
}

+static void vmballoon_add_page(struct vmballoon *b, int idx, struct page *p)
+{
+ b->page = p;
+}
+
+static void vmballoon_add_batched_page(struct vmballoon *b, int idx,
+ struct page *p)
+{
+ vmballoon_batch_set_pa(b->batch_page, idx,
+ (u64)page_to_pfn(p) << PAGE_SHIFT);
+}
+
/*
* Inflate the balloon towards its target size. Note that we try to limit
* the rate of allocation to make sure we are not choking the rest of the
@@ -507,6 +714,7 @@ static void vmballoon_inflate(struct vmballoon *b)
unsigned int rate;
unsigned int i;
unsigned int allocations = 0;
+ unsigned int num_pages = 0;
int error = 0;
gfp_t flags = VMW_PAGE_ALLOC_NOSLEEP;

@@ -539,14 +747,13 @@ static void vmballoon_inflate(struct vmballoon *b)
__func__, goal, rate, b->rate_alloc);

for (i = 0; i < goal; i++) {
- struct page *page;
+ struct page *page = alloc_page(flags);

if (flags == VMW_PAGE_ALLOC_NOSLEEP)
STATS_INC(b->stats.alloc);
else
STATS_INC(b->stats.sleep_alloc);

- page = alloc_page(flags);
if (!page) {
if (flags == VMW_PAGE_ALLOC_CANSLEEP) {
/*
@@ -580,9 +787,13 @@ static void vmballoon_inflate(struct vmballoon *b)
continue;
}

- error = vmballoon_lock_page(b, page);
- if (error)
- break;
+ b->ops->add_page(b, num_pages++, page);
+ if (num_pages == b->batch_max_pages) {
+ error = b->ops->lock(b, num_pages);
+ num_pages = 0;
+ if (error)
+ break;
+ }

if (++allocations > VMW_BALLOON_YIELD_THRESHOLD) {
cond_resched();
@@ -595,6 +806,9 @@ static void vmballoon_inflate(struct vmballoon *b)
}
}

+ if (num_pages > 0)
+ b->ops->lock(b, num_pages);
+
/*
* We reached our goal without failures so try increasing
* allocation rate.
@@ -618,6 +832,7 @@ static void vmballoon_deflate(struct vmballoon *b)
struct page *page, *next;
unsigned int i = 0;
unsigned int goal;
+ unsigned int num_pages = 0;
int error;

pr_debug("%s - size: %d, target %d\n", __func__, b->size, b->target);
@@ -629,21 +844,94 @@ static void vmballoon_deflate(struct vmballoon *b)

/* free pages to reach target */
list_for_each_entry_safe(page, next, &b->pages, lru) {
- error = vmballoon_release_page(b, page);
- if (error) {
- /* quickly decrease rate in case of error */
- b->rate_free = max(b->rate_free / 2,
- VMW_BALLOON_RATE_FREE_MIN);
- return;
+ 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);
+ 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);
+ return;
+ }
}

if (++i >= goal)
break;
}

+ if (num_pages > 0)
+ b->ops->unlock(b, num_pages);
+
/* slowly increase rate if there were no errors */
- b->rate_free = min(b->rate_free + VMW_BALLOON_RATE_FREE_INC,
- VMW_BALLOON_RATE_FREE_MAX);
+ 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 = {
+ .add_page = vmballoon_add_page,
+ .lock = vmballoon_lock_page,
+ .unlock = vmballoon_unlock_page
+};
+
+static const struct vmballoon_ops vmballoon_batched_ops = {
+ .add_page = vmballoon_add_batched_page,
+ .lock = vmballoon_lock_batched_page,
+ .unlock = vmballoon_unlock_batched_page
+};
+
+static bool vmballoon_init_batching(struct vmballoon *b)
+{
+ b->page = alloc_page(VMW_PAGE_ALLOC_NOSLEEP);
+ if (!b->page)
+ return false;
+
+ b->batch_page = vmap(&b->page, 1, VM_MAP, PAGE_KERNEL);
+ if (!b->batch_page) {
+ __free_page(b->page);
+ return false;
+ }
+
+ return true;
+}
+
+/*
+ * Perform standard reset sequence by popping the balloon (in case it
+ * is not empty) and then restarting protocol. This operation normally
+ * happens when host responds with VMW_BALLOON_ERROR_RESET to a command.
+ */
+static void vmballoon_reset(struct vmballoon *b)
+{
+ /* free all pages, skipping monitor unlock */
+ vmballoon_pop(b);
+
+ if (!vmballoon_send_start(b, VMW_BALLOON_CAPABILITIES))
+ return;
+
+ if ((b->capabilities & VMW_BALLOON_BATCHED_CMDS) != 0) {
+ b->ops = &vmballoon_batched_ops;
+ b->batch_max_pages = VMW_BALLOON_BATCH_MAX_PAGES;
+ if (!vmballoon_init_batching(b)) {
+ /*
+ * We failed to initialize batching, inform the monitor
+ * about it by sending a null capability.
+ *
+ * The guest will retry in one second.
+ */
+ vmballoon_send_start(b, 0);
+ return;
+ }
+ } else if ((b->capabilities & VMW_BALLOON_BASIC_CMDS) != 0) {
+ b->ops = &vmballoon_basic_ops;
+ b->batch_max_pages = 1;
+ }
+
+ b->reset_required = false;
+ if (!vmballoon_send_guest_id(b))
+ pr_err("failed to send guest ID to the host\n");
}

/*
@@ -802,11 +1090,23 @@ static int __init vmballoon_init(void)
/*
* Start balloon.
*/
- if (!vmballoon_send_start(&balloon)) {
+ if (!vmballoon_send_start(&balloon, VMW_BALLOON_CAPABILITIES)) {
pr_err("failed to send start command to the host\n");
return -EIO;
}

+ if ((balloon.capabilities & VMW_BALLOON_BATCHED_CMDS) != 0) {
+ balloon.ops = &vmballoon_batched_ops;
+ balloon.batch_max_pages = VMW_BALLOON_BATCH_MAX_PAGES;
+ if (!vmballoon_init_batching(&balloon)) {
+ pr_err("failed to init batching\n");
+ return -EIO;
+ }
+ } else if ((balloon.capabilities & VMW_BALLOON_BASIC_CMDS) != 0) {
+ balloon.ops = &vmballoon_basic_ops;
+ balloon.batch_max_pages = 1;
+ }
+
if (!vmballoon_send_guest_id(&balloon)) {
pr_err("failed to send guest ID to the host\n");
return -EIO;
@@ -833,7 +1133,7 @@ static void __exit vmballoon_exit(void)
* Reset connection before deallocating memory to avoid potential for
* additional spurious resets from guest touching deallocated pages.
*/
- vmballoon_send_start(&balloon);
+ vmballoon_send_start(&balloon, VMW_BALLOON_CAPABILITIES);
vmballoon_pop(&balloon);
}
module_exit(vmballoon_exit);
--
2.4.3