[PATCH -mm -v3] mm, swap: Use kvzalloc to allocate some swap data structure

[PATCH -mm -v3] mm, swap: Use kvzalloc to allocate some swap data structure

[Huang, Ying]

From: Huang Ying <ying.huang@intel.com>

Now vzalloc() is used in swap code to allocate various data
structures, such as swap cache, swap slots cache, cluster info, etc.
Because the size may be too large on some system, so that normal
kzalloc() may fail.  But using kzalloc() has some advantages, for
example, less memory fragmentation, less TLB pressure, etc.  So change
the data structure allocation in swap code to use kvzalloc() which
will try kzalloc() firstly, and fallback to vzalloc() if kzalloc()
failed.

In general, although kmalloc() will reduce the number of high-order
pages in short term, vmalloc() will cause more pain for memory
fragmentation in the long term.  And the swap data structure
allocation that is changed in this patch is expected to be long term
allocation.  From Dave Hansen: for example, we have a two-page data
structure.  vmalloc() takes two effectively random order-0 pages,
probably from two different 2M pages and pins them.  That "kills" two
2M pages.  kmalloc(), allocating two *contiguous* pages, will not
cross a 2M boundary.  That means it will only "kill" the possibility
of a single 2M page.  More 2M pages == less fragmentation.

The allocation in this patch occurs during swap on time, which is
usually done during system boot, so usually we have high opportunity
to allocate the contiguous pages successfully.

The allocation for swap_map[] in struct swap_info_struct is not
changed, because that is usually quite large and vmalloc_to_page() is
used for it.  That makes it a little harder to change.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Acked-by: Tim Chen <tim.c.chen@intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>

v3:

- Revise patch description

v2:

- Use common kvzalloc() instead of self-made swap_kvzalloc().
---
 mm/swap_slots.c | 19 +++++++++++--------
 mm/swap_state.c |  2 +-
 mm/swapfile.c   | 10 ++++++----
 3 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/mm/swap_slots.c b/mm/swap_slots.c
index aa1c415f4abd..58f6c78f1dad 100644
--- a/mm/swap_slots.c
+++ b/mm/swap_slots.c
@@ -31,6 +31,7 @@
 #include <linux/cpumask.h>
 #include <linux/vmalloc.h>
 #include <linux/mutex.h>
+#include <linux/mm.h>
 
 #ifdef CONFIG_SWAP
 
@@ -119,16 +120,18 @@ static int alloc_swap_slot_cache(unsigned int cpu)
 
 	/*
 	 * Do allocation outside swap_slots_cache_mutex
-	 * as vzalloc could trigger reclaim and get_swap_page,
+	 * as kvzalloc could trigger reclaim and get_swap_page,
 	 * which can lock swap_slots_cache_mutex.
 	 */
-	slots = vzalloc(sizeof(swp_entry_t) * SWAP_SLOTS_CACHE_SIZE);
+	slots = kvzalloc(sizeof(swp_entry_t) * SWAP_SLOTS_CACHE_SIZE,
+			 GFP_KERNEL);
 	if (!slots)
 		return -ENOMEM;
 
-	slots_ret = vzalloc(sizeof(swp_entry_t) * SWAP_SLOTS_CACHE_SIZE);
+	slots_ret = kvzalloc(sizeof(swp_entry_t) * SWAP_SLOTS_CACHE_SIZE,
+			     GFP_KERNEL);
 	if (!slots_ret) {
-		vfree(slots);
+		kvfree(slots);
 		return -ENOMEM;
 	}
 
@@ -152,9 +155,9 @@ static int alloc_swap_slot_cache(unsigned int cpu)
 out:
 	mutex_unlock(&swap_slots_cache_mutex);
 	if (slots)
-		vfree(slots);
+		kvfree(slots);
 	if (slots_ret)
-		vfree(slots_ret);
+		kvfree(slots_ret);
 	return 0;
 }
 
@@ -171,7 +174,7 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
 		cache->cur = 0;
 		cache->nr = 0;
 		if (free_slots && cache->slots) {
-			vfree(cache->slots);
+			kvfree(cache->slots);
 			cache->slots = NULL;
 		}
 		mutex_unlock(&cache->alloc_lock);
@@ -186,7 +189,7 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
 		}
 		spin_unlock_irq(&cache->free_lock);
 		if (slots)
-			vfree(slots);
+			kvfree(slots);
 	}
 }
 
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 7bfb9bd1ca21..539b8885e3d1 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -523,7 +523,7 @@ int init_swap_address_space(unsigned int type, unsigned long nr_pages)
 	unsigned int i, nr;
 
 	nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
-	spaces = vzalloc(sizeof(struct address_space) * nr);
+	spaces = kvzalloc(sizeof(struct address_space) * nr, GFP_KERNEL);
 	if (!spaces)
 		return -ENOMEM;
 	for (i = 0; i < nr; i++) {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 53b5881ee0d6..90054f3c2cdc 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2272,8 +2272,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	free_percpu(p->percpu_cluster);
 	p->percpu_cluster = NULL;
 	vfree(swap_map);
-	vfree(cluster_info);
-	vfree(frontswap_map);
+	kvfree(cluster_info);
+	kvfree(frontswap_map);
 	/* Destroy swap account information */
 	swap_cgroup_swapoff(p->type);
 	exit_swap_address_space(p->type);
@@ -2796,7 +2796,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		p->cluster_next = 1 + (prandom_u32() % p->highest_bit);
 		nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
 
-		cluster_info = vzalloc(nr_cluster * sizeof(*cluster_info));
+		cluster_info = kvzalloc(nr_cluster * sizeof(*cluster_info),
+					GFP_KERNEL);
 		if (!cluster_info) {
 			error = -ENOMEM;
 			goto bad_swap;
@@ -2829,7 +2830,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	}
 	/* frontswap enabled? set up bit-per-page map for frontswap */
 	if (IS_ENABLED(CONFIG_FRONTSWAP))
-		frontswap_map = vzalloc(BITS_TO_LONGS(maxpages) * sizeof(long));
+		frontswap_map = kvzalloc(BITS_TO_LONGS(maxpages) * sizeof(long),
+					 GFP_KERNEL);
 
 	if (p->bdev &&(swap_flags & SWAP_FLAG_DISCARD) && swap_discardable(p)) {
 		/*
-- 
2.11.0

Re: [PATCH -mm -v3] mm, swap: Use kvzalloc to allocate some swap data structure

[Rik van Riel]

On Fri, 2017-04-07 at 14:49 +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> Now vzalloc() is used in swap code to allocate various data
> structures, such as swap cache, swap slots cache, cluster info, etc.
> Because the size may be too large on some system, so that normal
> kzalloc() may fail.  But using kzalloc() has some advantages,

> Signed-off-by: Huang Ying <ying.huang@intel.com>
> Acked-by: Tim Chen <tim.c.chen@intel.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Shaohua Li <shli@kernel.org>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Rik van Riel <riel@redhat.com>
> 
Acked-by: Rik van Riel <riel@redhat.com>