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Subject[PATCH V2 2/2] zswap: Add module parameter malloc_movable_if_support
Date
This is the second version that was updated according to the comments
from Sergey Senozhatsky in https://lkml.org/lkml/2019/5/29/73

zswap compresses swap pages into a dynamically allocated RAM-based
memory pool. The memory pool should be zbud, z3fold or zsmalloc.
All of them will allocate unmovable pages. It will increase the
number of unmovable page blocks that will bad for anti-fragment.

zsmalloc support page migration if request movable page:
handle = zs_malloc(zram->mem_pool, comp_len,
GFP_NOIO | __GFP_HIGHMEM |
__GFP_MOVABLE);

And commit "zpool: Add malloc_support_movable to zpool_driver" add
zpool_malloc_support_movable check malloc_support_movable to make
sure if a zpool support allocate movable memory.

This commit adds module parameter malloc_movable_if_support to enable
or disable zpool allocate block with gfp __GFP_HIGHMEM | __GFP_MOVABLE
if it support allocate movable memory (disabled by default).

Following part is test log in a pc that has 8G memory and 2G swap.

When it disabled:
echo lz4 > /sys/module/zswap/parameters/compressor
echo zsmalloc > /sys/module/zswap/parameters/zpool
echo 1 > /sys/module/zswap/parameters/enabled
swapon /swapfile
cd /home/teawater/kernel/vm-scalability/
/home/teawater/kernel/vm-scalability# export unit_size=$((9 * 1024 * 1024 * 1024))
/home/teawater/kernel/vm-scalability# ./case-anon-w-seq
2717908992 bytes / 3977932 usecs = 667233 KB/s
2717908992 bytes / 4160702 usecs = 637923 KB/s
2717908992 bytes / 4354611 usecs = 609516 KB/s
293359 usecs to free memory
340304 usecs to free memory
205781 usecs to free memory
2717908992 bytes / 5588016 usecs = 474982 KB/s
166124 usecs to free memory
/home/teawater/kernel/vm-scalability# cat /proc/pagetypeinfo
Page block order: 9
Pages per block: 512

Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
Node 0, zone DMA, type Unmovable 1 1 1 0 2 1 1 0 1 0 0
Node 0, zone DMA, type Movable 0 0 0 0 0 0 0 0 0 1 3
Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type Unmovable 5 10 9 8 8 5 1 2 3 0 0
Node 0, zone DMA32, type Movable 15 16 14 12 14 10 9 6 6 5 776
Node 0, zone DMA32, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Unmovable 7097 6914 6473 5642 4373 2664 1220 319 78 4 0
Node 0, zone Normal, type Movable 2092 3216 2820 2266 1585 946 559 359 237 258 378
Node 0, zone Normal, type Reclaimable 47 88 122 80 34 9 5 4 2 1 2
Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0

Number of blocks type Unmovable Movable Reclaimable HighAtomic CMA Isolate
Node 0, zone DMA 1 7 0 0 0 0
Node 0, zone DMA32 4 1652 0 0 0 0
Node 0, zone Normal 834 1572 25 0 0 0

When it enabled:
echo lz4 > /sys/module/zswap/parameters/compressor
echo zsmalloc > /sys/module/zswap/parameters/zpool
echo 1 > /sys/module/zswap/parameters/enabled
echo 1 > /sys/module/zswap/parameters/malloc_movable_if_support
swapon /swapfile
cd /home/teawater/kernel/vm-scalability/
/home/teawater/kernel/vm-scalability# export unit_size=$((9 * 1024 * 1024 * 1024))
/home/teawater/kernel/vm-scalability# ./case-anon-w-seq
2717908992 bytes / 4721401 usecs = 562165 KB/s
2717908992 bytes / 4783167 usecs = 554905 KB/s
2717908992 bytes / 4802125 usecs = 552715 KB/s
2717908992 bytes / 4866579 usecs = 545395 KB/s
323605 usecs to free memory
414817 usecs to free memory
458576 usecs to free memory
355827 usecs to free memory
/home/teawater/kernel/vm-scalability# cat /proc/pagetypeinfo
Page block order: 9
Pages per block: 512

Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
Node 0, zone DMA, type Unmovable 1 1 1 0 2 1 1 0 1 0 0
Node 0, zone DMA, type Movable 0 0 0 0 0 0 0 0 0 1 3
Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type Unmovable 8 10 8 7 7 6 5 3 2 0 0
Node 0, zone DMA32, type Movable 23 21 18 15 13 14 14 10 11 6 766
Node 0, zone DMA32, type Reclaimable 0 0 0 0 0 0 0 0 0 0 1
Node 0, zone DMA32, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Unmovable 2660 1295 460 102 11 5 3 11 2 4 0
Node 0, zone Normal, type Movable 4178 5760 5045 4137 3324 2306 1482 930 497 254 460
Node 0, zone Normal, type Reclaimable 50 83 114 93 28 12 10 6 3 3 0
Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0

Number of blocks type Unmovable Movable Reclaimable HighAtomic CMA Isolate
Node 0, zone DMA 1 7 0 0 0 0
Node 0, zone DMA32 4 1650 2 0 0 0
Node 0, zone Normal 81 2325 25 0 0 0

You can see that the number of unmovable page blocks is decreased
when malloc_movable_if_support is enabled.

Signed-off-by: Hui Zhu <teawaterz@linux.alibaba.com>
---
mm/zswap.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index a4e4d36ec085..2fc45de92383 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -123,6 +123,13 @@ static bool zswap_same_filled_pages_enabled = true;
module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
bool, 0644);

+/* Enable/disable zpool allocate block with gfp __GFP_HIGHMEM | __GFP_MOVABLE
+ * if it support allocate movable memory (disabled by default).
+ */
+static bool __read_mostly zswap_malloc_movable_if_support;
+module_param_cb(malloc_movable_if_support, &param_ops_bool,
+ &zswap_malloc_movable_if_support, 0644);
+
/*********************************
* data structures
**********************************/
@@ -1006,6 +1013,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
char *buf;
u8 *src, *dst;
struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
+ gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;

/* THP isn't supported */
if (PageTransHuge(page)) {
@@ -1079,9 +1087,11 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,

/* store */
hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
- ret = zpool_malloc(entry->pool->zpool, hlen + dlen,
- __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
- &handle);
+ if (zswap_malloc_movable_if_support &&
+ zpool_malloc_support_movable(entry->pool->zpool)) {
+ gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
+ }
+ ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
if (ret == -ENOSPC) {
zswap_reject_compress_poor++;
goto put_dstmem;
--
2.20.1 (Apple Git-117)
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