[PATCH v1 07/12] powerpc/pseries: CMM: Convert loaned_pages to an atomic_long_t

David Hildenbrand
2019-10-31T14:30:31Z

When switching to balloon compaction, we want to drop the cmm_lock and
completely rely on the balloon compaction list lock internally.
loaned_pages is currently protected under the cmm_lock.

Note: Right now cmm_alloc_pages() and cmm_free_pages() can be called at
the same time, e.g., via the thread and a concurrent OOM notifier.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Richard Fontana <rfontana@redhat.com>
Cc: Allison Randal <allison@lohutok.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arun KS <arunks@codeaurora.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/powerpc/platforms/pseries/cmm.c | 35 +++++++++++++++-------------
1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/cmm.c b/arch/powerpc/platforms/pseries/cmm.c
index 29416b621189..3a55dd1fdd39 100644
--- a/arch/powerpc/platforms/pseries/cmm.c
+++ b/arch/powerpc/platforms/pseries/cmm.c
@@ -73,7 +73,7 @@ MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. "

#define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); }

-static unsigned long loaned_pages;
+static atomic_long_t loaned_pages;
static unsigned long loaned_pages_target;
static unsigned long oom_freed_pages;

@@ -159,7 +159,7 @@ static long cmm_alloc_pages(long nr)
}

list_add(&page->lru, &cmm_page_list);
- loaned_pages++;
+ atomic_long_inc(&loaned_pages);
adjust_managed_page_count(page, -1);
spin_unlock(&cmm_lock);
nr--;
@@ -189,7 +189,7 @@ static long cmm_free_pages(long nr)
list_del(&page->lru);
adjust_managed_page_count(page, 1);
__free_page(page);
- loaned_pages--;
+ atomic_long_dec(&loaned_pages);
nr--;
}
spin_unlock(&cmm_lock);
@@ -214,7 +214,7 @@ static int cmm_oom_notify(struct notifier_block *self,

cmm_dbg("OOM processing started\n");
nr = cmm_free_pages(nr);
- loaned_pages_target = loaned_pages;
+ loaned_pages_target = atomic_long_read(&loaned_pages);
*freed += KB2PAGES(oom_kb) - nr;
oom_freed_pages += KB2PAGES(oom_kb) - nr;
cmm_dbg("OOM processing complete\n");
@@ -231,10 +231,11 @@ static int cmm_oom_notify(struct notifier_block *self,
**/
static void cmm_get_mpp(void)
{
+ const long __loaned_pages = atomic_long_read(&loaned_pages);
+ const long total_pages = totalram_pages() + __loaned_pages;
int rc;
struct hvcall_mpp_data mpp_data;
signed long active_pages_target, page_loan_request, target;
- signed long total_pages = totalram_pages() + loaned_pages;
signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE;

rc = h_get_mpp(&mpp_data);
@@ -243,7 +244,7 @@ static void cmm_get_mpp(void)
return;

page_loan_request = div_s64((s64)mpp_data.loan_request, PAGE_SIZE);
- target = page_loan_request + (signed long)loaned_pages;
+ target = page_loan_request + __loaned_pages;

if (target < 0 || total_pages < min_mem_pages)
target = 0;
@@ -264,7 +265,7 @@ static void cmm_get_mpp(void)
loaned_pages_target = target;

cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu\n",
- page_loan_request, loaned_pages, loaned_pages_target,
+ page_loan_request, __loaned_pages, loaned_pages_target,
oom_freed_pages, totalram_pages());
}

@@ -282,6 +283,7 @@ static struct notifier_block cmm_oom_nb = {
static int cmm_thread(void *dummy)
{
unsigned long timeleft;
+ long __loaned_pages;

while (1) {
timeleft = msleep_interruptible(delay * 1000);
@@ -312,11 +314,12 @@ static int cmm_thread(void *dummy)

cmm_get_mpp();

- if (loaned_pages_target > loaned_pages) {
- if (cmm_alloc_pages(loaned_pages_target - loaned_pages))
- loaned_pages_target = loaned_pages;
- } else if (loaned_pages_target < loaned_pages)
- cmm_free_pages(loaned_pages - loaned_pages_target);
+ __loaned_pages = atomic_long_read(&loaned_pages);
+ if (loaned_pages_target > __loaned_pages) {
+ if (cmm_alloc_pages(loaned_pages_target - __loaned_pages))
+ loaned_pages_target = __loaned_pages;
+ } else if (loaned_pages_target < __loaned_pages)
+ cmm_free_pages(__loaned_pages - loaned_pages_target);
}
return 0;
}
@@ -330,7 +333,7 @@ static int cmm_thread(void *dummy)
} \
static DEVICE_ATTR(name, 0444, show_##name, NULL)

-CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(loaned_pages));
+CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(atomic_long_read(&loaned_pages)));
CMM_SHOW(loaned_target_kb, "%lu\n", PAGES2KB(loaned_pages_target));

static ssize_t show_oom_pages(struct device *dev,
@@ -433,7 +436,7 @@ static int cmm_reboot_notifier(struct notifier_block *nb,
if (cmm_thread_ptr)
kthread_stop(cmm_thread_ptr);
cmm_thread_ptr = NULL;
- cmm_free_pages(loaned_pages);
+ cmm_free_pages(atomic_long_read(&loaned_pages));
}
return NOTIFY_DONE;
}
@@ -540,7 +543,7 @@ static void cmm_exit(void)
unregister_oom_notifier(&cmm_oom_nb);
unregister_reboot_notifier(&cmm_reboot_nb);
unregister_memory_notifier(&cmm_mem_nb);
- cmm_free_pages(loaned_pages);
+ cmm_free_pages(atomic_long_read(&loaned_pages));
cmm_unregister_sysfs(&cmm_dev);
}

@@ -561,7 +564,7 @@ static int cmm_set_disable(const char *val, const struct kernel_param *kp)
if (cmm_thread_ptr)
kthread_stop(cmm_thread_ptr);
cmm_thread_ptr = NULL;
- cmm_free_pages(loaned_pages);
+ cmm_free_pages(atomic_long_read(&loaned_pages));
} else if (!disable && cmm_disabled) {
cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
if (IS_ERR(cmm_thread_ptr))
--
2.21.0