Replace the synchronous `submit_bio_wait()` with the non-blocking
`submit_bio()` to perform writeback operations asynchronously. This
leverages the infrastructure added in the previous commit to handle
the completion of I/O operations in a dedicated kthread.
This change shows 27% speed improvement of idle writeback on Android
platform.
Test Flow:
- mkfs on the zram device, mount it
- cp three linux-6.16-rc2.tar.gz tarball files as the data
- do idle writeback
- check bd_stat writes 185072 pages
Test Result:
idle writeback for 185072 4k-pages (~723 MiB)
$ echo all > /sys/block/zram0/idle
$ time echo idle > /sys/block/zram0/writeback
Async writeback:
0m02.49s real 0m00.00s user 0m01.19s system
0m02.32s real 0m00.00s user 0m00.89s system
0m02.35s real 0m00.00s user 0m00.93s system
0m02.29s real 0m00.00s user 0m00.88s system
Sync writeback:
0m03.09s real 0m00.00s user 0m01.07s system
0m03.18s real 0m00.00s user 0m01.12s system
0m03.47s real 0m00.00s user 0m01.16s system
0m03.36s real 0m00.00s user 0m01.27s system
Signed-off-by: Richard Chang <richardycc@xxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 109 ++++++++++++++--------------------
drivers/block/zram/zram_drv.h | 11 ++++
drivers/block/zram/zram_wb.c | 103 +++++++++++++++++++++++++++++++-
drivers/block/zram/zram_wb.h | 6 +-
4 files changed, 161 insertions(+), 68 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 6098c0bb773c..f459d889fa44 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -57,7 +57,6 @@ static size_t huge_class_size;
static const struct block_device_operations zram_devops;
-static void zram_free_page(struct zram *zram, size_t index);
static int zram_read_from_zspool(struct zram *zram, struct page *page,
u32 index);
@@ -96,7 +95,7 @@ static __must_check bool zram_slot_trylock(struct zram *zram, u32 index)
return false;
}
-static void zram_slot_lock(struct zram *zram, u32 index)
+void zram_slot_lock(struct zram *zram, u32 index)
{
unsigned long *lock = &zram->table[index].flags;
@@ -105,7 +104,7 @@ static void zram_slot_lock(struct zram *zram, u32 index)
lock_acquired(slot_dep_map(zram, index), _RET_IP_);
}
-static void zram_slot_unlock(struct zram *zram, u32 index)
+void zram_slot_unlock(struct zram *zram, u32 index)
{
unsigned long *lock = &zram->table[index].flags;
@@ -128,19 +127,17 @@ static unsigned long zram_get_handle(struct zram *zram, u32 index)
return zram->table[index].handle;
}
-static void zram_set_handle(struct zram *zram, u32 index, unsigned long handle)
+void zram_set_handle(struct zram *zram, u32 index, unsigned long handle)
{
zram->table[index].handle = handle;
}
-static bool zram_test_flag(struct zram *zram, u32 index,
- enum zram_pageflags flag)
+bool zram_test_flag(struct zram *zram, u32 index, enum zram_pageflags flag)
{
return zram->table[index].flags & BIT(flag);
}
-static void zram_set_flag(struct zram *zram, u32 index,
- enum zram_pageflags flag)
+void zram_set_flag(struct zram *zram, u32 index, enum zram_pageflags flag)
{
zram->table[index].flags |= BIT(flag);
}
@@ -243,15 +240,20 @@ static struct zram_pp_ctl *init_pp_ctl(void)
if (!ctl)
return NULL;
+ init_completion(&ctl->all_done);
+ atomic_set(&ctl->num_pp_slots, 0);
for (idx = 0; idx < NUM_PP_BUCKETS; idx++)
INIT_LIST_HEAD(&ctl->pp_buckets[idx]);
return ctl;
}
-static void release_pp_slot(struct zram *zram, struct zram_pp_slot *pps)
+static void remove_pp_slot_from_ctl(struct zram_pp_slot *pps)
{
list_del_init(&pps->entry);
+}
+void free_pp_slot(struct zram *zram, struct zram_pp_slot *pps)
+{
zram_slot_lock(zram, pps->index);
zram_clear_flag(zram, pps->index, ZRAM_PP_SLOT);
zram_slot_unlock(zram, pps->index);
@@ -259,6 +261,12 @@ static void release_pp_slot(struct zram *zram, struct zram_pp_slot *pps)
kfree(pps);
}
+static void release_pp_slot(struct zram *zram, struct zram_pp_slot *pps)
+{
+ remove_pp_slot_from_ctl(pps);
+ free_pp_slot(zram, pps);
+}
+
static void release_pp_ctl(struct zram *zram, struct zram_pp_ctl *ctl)
{
u32 idx;
@@ -297,6 +305,7 @@ static bool place_pp_slot(struct zram *zram, struct zram_pp_ctl *ctl,
list_add(&pps->entry, &ctl->pp_buckets[bid]);
zram_set_flag(zram, pps->index, ZRAM_PP_SLOT);
+ atomic_inc(&ctl->num_pp_slots);
return true;
}
@@ -697,18 +706,18 @@ static void read_from_bdev_async(struct zram *zram, struct page *page,
static int zram_writeback_slots(struct zram *zram, struct zram_pp_ctl *ctl)
{
unsigned long blk_idx = 0;
- struct page *page = NULL;
struct zram_pp_slot *pps;
- struct bio_vec bio_vec;
- struct bio bio;
- int ret = 0, err;
+ int ret = 0;
u32 index;
+ int nr_pps = atomic_read(&ctl->num_pp_slots);
- page = alloc_page(GFP_KERNEL);
- if (!page)
- return -ENOMEM;
+ if (!nr_pps)
+ return 0;
while ((pps = select_pp_slot(ctl))) {
+ struct zram_wb_request *req;
+ struct page *page;
+
spin_lock(&zram->wb_limit_lock);
if (zram->wb_limit_enable && !zram->bd_wb_limit) {
spin_unlock(&zram->wb_limit_lock);
@@ -725,6 +734,13 @@ static int zram_writeback_slots(struct zram *zram, struct zram_pp_ctl *ctl)
}
}
+ req = alloc_wb_request(zram, pps, ctl, blk_idx);
+ if (IS_ERR(req)) {
+ ret = PTR_ERR(req);
+ break;
+ }
+ page = bio_first_page_all(req->bio);
+
index = pps->index;
zram_slot_lock(zram, index);
/*
@@ -739,63 +755,28 @@ static int zram_writeback_slots(struct zram *zram, struct zram_pp_ctl *ctl)
goto next;
zram_slot_unlock(zram, index);
- bio_init(&bio, zram->bdev, &bio_vec, 1,
- REQ_OP_WRITE | REQ_SYNC);
- bio.bi_iter.bi_sector = blk_idx * (PAGE_SIZE >> 9);
- __bio_add_page(&bio, page, PAGE_SIZE, 0);
-
- /*
- * XXX: A single page IO would be inefficient for write
- * but it would be not bad as starter.
- */
- err = submit_bio_wait(&bio);
- if (err) {
- release_pp_slot(zram, pps);
- /*
- * BIO errors are not fatal, we continue and simply
- * attempt to writeback the remaining objects (pages).
- * At the same time we need to signal user-space that
- * some writes (at least one, but also could be all of
- * them) were not successful and we do so by returning
- * the most recent BIO error.
- */
- ret = err;
- continue;
- }
-
- atomic64_inc(&zram->stats.bd_writes);
- zram_slot_lock(zram, index);
- /*
- * Same as above, we release slot lock during writeback so
- * slot can change under us: slot_free() or slot_free() and
- * reallocation (zram_write_page()). In both cases slot loses
- * ZRAM_PP_SLOT flag. No concurrent post-processing can set
- * ZRAM_PP_SLOT on such slots until current post-processing
- * finishes.
- */
- if (!zram_test_flag(zram, index, ZRAM_PP_SLOT))
- goto next;
-
- zram_free_page(zram, index);
- zram_set_flag(zram, index, ZRAM_WB);
- zram_set_handle(zram, index, blk_idx);
+ nr_pps--;
+ remove_pp_slot_from_ctl(pps);
blk_idx = 0;
- atomic64_inc(&zram->stats.pages_stored);
- spin_lock(&zram->wb_limit_lock);
- if (zram->wb_limit_enable && zram->bd_wb_limit > 0)
- zram->bd_wb_limit -= 1UL << (PAGE_SHIFT - 12);
- spin_unlock(&zram->wb_limit_lock);
+ submit_bio(req->bio);
+ continue;
+
next:
zram_slot_unlock(zram, index);
release_pp_slot(zram, pps);
+ free_wb_request(req);
cond_resched();
}
if (blk_idx)
free_block_bdev(zram, blk_idx);
- if (page)
- __free_page(page);
+
+ if (nr_pps && atomic_sub_and_test(nr_pps, &ctl->num_pp_slots))
+ complete(&ctl->all_done);
+
+ /* wait until all async bios completed */
+ wait_for_completion(&ctl->all_done);
return ret;
}
@@ -1579,7 +1560,7 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
return true;
}
-static void zram_free_page(struct zram *zram, size_t index)
+void zram_free_page(struct zram *zram, size_t index)
{
unsigned long handle;
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 2c7bc05fb186..ab5ceecc8ed8 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -140,6 +140,13 @@ struct zram {
atomic_t pp_in_progress;
};
+void zram_slot_lock(struct zram *zram, u32 index);
+void zram_slot_unlock(struct zram *zram, u32 index);
+void zram_set_handle(struct zram *zram, u32 index, unsigned long handle);
+bool zram_test_flag(struct zram *zram, u32 index, enum zram_pageflags flag);
+void zram_set_flag(struct zram *zram, u32 index, enum zram_pageflags flag);
+void zram_free_page(struct zram *zram, size_t index);
+
#if defined CONFIG_ZRAM_WRITEBACK || defined CONFIG_ZRAM_MULTI_COMP
struct zram_pp_slot {
unsigned long index;
@@ -155,7 +162,11 @@ struct zram_pp_slot {
struct zram_pp_ctl {
struct list_head pp_buckets[NUM_PP_BUCKETS];
+ struct completion all_done;
+ atomic_t num_pp_slots;
};
+
+void free_pp_slot(struct zram *zram, struct zram_pp_slot *pps);
#endif
#endif
diff --git a/drivers/block/zram/zram_wb.c b/drivers/block/zram/zram_wb.c
index 63a16dae5796..3b8edd048dcb 100644
--- a/drivers/block/zram/zram_wb.c
+++ b/drivers/block/zram/zram_wb.c
@@ -43,15 +43,60 @@ void free_block_bdev(struct zram *zram, unsigned long blk_idx)
static void complete_wb_request(struct zram_wb_request *req)
{
struct zram *zram = req->zram;
+ struct zram_pp_slot *pps = req->pps;
+ struct zram_pp_ctl *ctl = req->ppctl;
+ unsigned long index = pps->index;
unsigned long blk_idx = req->blk_idx;
+ struct bio *bio = req->bio;
+
+ if (bio->bi_status)
+ goto out_err;
+
+ atomic64_inc(&zram->stats.bd_writes);
+ zram_slot_lock(zram, index);
+
+ /*
+ * We release slot lock during writeback so slot can change
+ * under us: slot_free() or slot_free() and reallocation
+ * (zram_write_page()). In both cases slot loses
+ * ZRAM_PP_SLOT flag. No concurrent post-processing can set
+ * ZRAM_PP_SLOT on such slots until current post-processing
+ * finishes.
+ */
+ if (!zram_test_flag(zram, index, ZRAM_PP_SLOT)) {
+ zram_slot_unlock(zram, index);
+ goto out_err;
+ }
+ zram_free_page(zram, index);
+ zram_set_flag(zram, index, ZRAM_WB);
+ zram_set_handle(zram, index, blk_idx);
+ atomic64_inc(&zram->stats.pages_stored);
+ spin_lock(&zram->wb_limit_lock);
+ if (zram->wb_limit_enable && zram->bd_wb_limit > 0)
+ zram->bd_wb_limit -= 1UL << (PAGE_SHIFT - 12);
+ spin_unlock(&zram->wb_limit_lock);
+ zram_slot_unlock(zram, index);
+ goto end;
+
+out_err:
free_block_bdev(zram, blk_idx);
+end:
+ free_pp_slot(zram, pps);
free_wb_request(req);
+
+ if (atomic_dec_and_test(&ctl->num_pp_slots))
+ complete(&ctl->all_done);
}
-void enqueue_wb_request(struct zram_wb_request_list *req_list,
- struct zram_wb_request *req)
+static void enqueue_wb_request(struct zram_wb_request_list *req_list,
+ struct zram_wb_request *req)
{
+ /*
+ * The enqueue path comes from softirq context:
+ * blk_done_softirq -> bio_endio -> zram_writeback_end_io
+ * Use spin_lock_bh for locking.
+ */
spin_lock_bh(&req_list->lock);
list_add_tail(&req->node, &req_list->head);
req_list->count++;
@@ -83,6 +128,7 @@ static void destroy_wb_request_list(struct zram_wb_request_list *req_list)
while (!list_empty(&req_list->head)) {
req = dequeue_wb_request(req_list);
free_block_bdev(req->zram, req->blk_idx);
+ free_pp_slot(req->zram, req->pps);
free_wb_request(req);
}
}
@@ -117,6 +163,59 @@ static int wb_thread_func(void *data)
return 0;
}
+static void zram_writeback_end_io(struct bio *bio)
+{
+ struct zram_wb_request *req =
+ (struct zram_wb_request *)bio->bi_private;
+
+ enqueue_wb_request(&wb_req_list, req);
+ wake_up(&wb_wq);
+}
+
+struct zram_wb_request *alloc_wb_request(struct zram *zram,
+ struct zram_pp_slot *pps,
+ struct zram_pp_ctl *ppctl,
+ unsigned long blk_idx)
+{
+ struct zram_wb_request *req;
+ struct page *page;
+ struct bio *bio;
+ int err = 0;
+
+ page = alloc_page(GFP_NOIO | __GFP_NOWARN);
+ if (!page)
+ return ERR_PTR(-ENOMEM);
+
+ bio = bio_alloc(zram->bdev, 1, REQ_OP_WRITE, GFP_NOIO | __GFP_NOWARN);
+ if (!bio) {
+ err = -ENOMEM;
+ goto out_free_page;
+ }
+
+ req = kmalloc(sizeof(struct zram_wb_request), GFP_NOIO | __GFP_NOWARN);
+ if (!req) {
+ err = -ENOMEM;
+ goto out_free_bio;
+ }
+ req->zram = zram;
+ req->pps = pps;
+ req->ppctl = ppctl;
+ req->blk_idx = blk_idx;
+ req->bio = bio;
+
+ bio->bi_iter.bi_sector = blk_idx * (PAGE_SIZE >> 9);
+ __bio_add_page(bio, page, PAGE_SIZE, 0);
+ bio->bi_private = req;
+ bio->bi_end_io = zram_writeback_end_io;
+ return req;
+
+out_free_bio:
+ bio_put(bio);
+out_free_page:
+ __free_page(page);
+ return ERR_PTR(err);
+}
+
void free_wb_request(struct zram_wb_request *req)
{
struct bio *bio = req->bio;
diff --git a/drivers/block/zram/zram_wb.h b/drivers/block/zram/zram_wb.h
index b86de0398346..f6fe7c51d496 100644
--- a/drivers/block/zram/zram_wb.h
+++ b/drivers/block/zram/zram_wb.h
@@ -26,9 +26,11 @@ unsigned long alloc_block_bdev(struct zram *zram);
void free_block_bdev(struct zram *zram, unsigned long blk_idx);
int setup_zram_writeback(void);
void destroy_zram_writeback(void);
+struct zram_wb_request *alloc_wb_request(struct zram *zram,
+ struct zram_pp_slot *pps,
+ struct zram_pp_ctl *ppctl,
+ unsigned long blk_idx);
void free_wb_request(struct zram_wb_request *req);
-void enqueue_wb_request(struct zram_wb_request_list *req_list,
- struct zram_wb_request *req);
#else
inline unsigned long alloc_block_bdev(struct zram *zram) { return 0; }
inline void free_block_bdev(struct zram *zram, unsigned long blk_idx) {};
--
2.50.1.565.gc32cd1483b-goog
