Introduce writeback_batch_size device attribute so that
the maximum number of in-flight writeback bio requests
can be configured at run-time per-device. This essentially
enables batched bio writeback.
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
drivers/block/zram/zram_drv.c | 48 ++++++++++++++++++++++++++++++-----
drivers/block/zram/zram_drv.h | 1 +
2 files changed, 43 insertions(+), 6 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 37c1416ac902..7904159e9226 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -588,6 +588,42 @@ static ssize_t writeback_limit_show(struct device *dev,
return sysfs_emit(buf, "%llu\n", val);
}
+static ssize_t writeback_batch_size_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t len)
+{
+ struct zram *zram = dev_to_zram(dev);
+ u32 val;
+ ssize_t ret = -EINVAL;
+
+ if (kstrtouint(buf, 10, &val))
+ return ret;
+
+ if (!val)
+ val = 1;
+
+ down_read(&zram->init_lock);
+ zram->wb_batch_size = val;
+ up_read(&zram->init_lock);
+ ret = len;
+
+ return ret;
+}
+
+static ssize_t writeback_batch_size_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ u32 val;
+ struct zram *zram = dev_to_zram(dev);
+
+ down_read(&zram->init_lock);
+ val = zram->wb_batch_size;
+ up_read(&zram->init_lock);
+
+ return sysfs_emit(buf, "%u\n", val);
+}
+
static void reset_bdev(struct zram *zram)
{
if (!zram->backing_dev)
@@ -779,10 +815,7 @@ static void release_wb_ctl(struct zram_wb_ctl *wb_ctl)
kfree(wb_ctl);
}
-/* XXX: should be a per-device sysfs attr */
-#define ZRAM_WB_REQ_CNT 32
-
-static struct zram_wb_ctl *init_wb_ctl(void)
+static struct zram_wb_ctl *init_wb_ctl(struct zram *zram)
{
struct zram_wb_ctl *wb_ctl;
int i;
@@ -797,7 +830,7 @@ static struct zram_wb_ctl *init_wb_ctl(void)
init_waitqueue_head(&wb_ctl->done_wait);
spin_lock_init(&wb_ctl->done_lock);
- for (i = 0; i < ZRAM_WB_REQ_CNT; i++) {
+ for (i = 0; i < zram->wb_batch_size; i++) {
struct zram_wb_req *req;
/*
@@ -1197,7 +1230,7 @@ static ssize_t writeback_store(struct device *dev,
goto release_init_lock;
}
- wb_ctl = init_wb_ctl();
+ wb_ctl = init_wb_ctl(zram);
if (!wb_ctl) {
ret = -ENOMEM;
goto release_init_lock;
@@ -2840,6 +2873,7 @@ static DEVICE_ATTR_RW(backing_dev);
static DEVICE_ATTR_WO(writeback);
static DEVICE_ATTR_RW(writeback_limit);
static DEVICE_ATTR_RW(writeback_limit_enable);
+static DEVICE_ATTR_RW(writeback_batch_size);
#endif
#ifdef CONFIG_ZRAM_MULTI_COMP
static DEVICE_ATTR_RW(recomp_algorithm);
@@ -2861,6 +2895,7 @@ static struct attribute *zram_disk_attrs[] = {
&dev_attr_writeback.attr,
&dev_attr_writeback_limit.attr,
&dev_attr_writeback_limit_enable.attr,
+ &dev_attr_writeback_batch_size.attr,
#endif
&dev_attr_io_stat.attr,
&dev_attr_mm_stat.attr,
@@ -2922,6 +2957,7 @@ static int zram_add(void)
init_rwsem(&zram->init_lock);
#ifdef CONFIG_ZRAM_WRITEBACK
+ zram->wb_batch_size = 32;
spin_lock_init(&zram->wb_limit_lock);
#endif
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 6cee93f9c0d0..1a647f42c1a4 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -129,6 +129,7 @@ struct zram {
struct file *backing_dev;
spinlock_t wb_limit_lock;
bool wb_limit_enable;
+ u32 wb_batch_size;
u64 bd_wb_limit;
struct block_device *bdev;
unsigned long *bitmap;
--
2.52.0.rc1.455.g30608eb744-googOn (25/11/21 00:21), Sergey Senozhatsky wrote:
> +static ssize_t writeback_batch_size_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t len)
> +{
> + struct zram *zram = dev_to_zram(dev);
> + u32 val;
> + ssize_t ret = -EINVAL;
> +
> + if (kstrtouint(buf, 10, &val))
> + return ret;
> +
> + if (!val)
> + val = 1;
> +
> + down_read(&zram->init_lock);
> + zram->wb_batch_size = val;
> + up_read(&zram->init_lock);
> + ret = len;
> +
> + return ret;
> +}
JFI, as was suggested by Andrew in v4 thread, this should use write
lock.
On Thu, Nov 20, 2025 at 10:22 AM Sergey Senozhatsky
<senozhatsky@chromium.org> wrote:
>
> Introduce writeback_batch_size device attribute so that
> the maximum number of in-flight writeback bio requests
> can be configured at run-time per-device. This essentially
> enables batched bio writeback.
>
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
> drivers/block/zram/zram_drv.c | 48 ++++++++++++++++++++++++++++++-----
> drivers/block/zram/zram_drv.h | 1 +
> 2 files changed, 43 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 37c1416ac902..7904159e9226 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -588,6 +588,42 @@ static ssize_t writeback_limit_show(struct device *dev,
> return sysfs_emit(buf, "%llu\n", val);
> }
>
> +static ssize_t writeback_batch_size_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t len)
> +{
> + struct zram *zram = dev_to_zram(dev);
> + u32 val;
> + ssize_t ret = -EINVAL;
> +
> + if (kstrtouint(buf, 10, &val))
> + return ret;
> +
> + if (!val)
> + val = 1;
IMO a value of 0 for the batch size doesn't make sense, -EINVAL?
> +
> + down_read(&zram->init_lock);
> + zram->wb_batch_size = val;
> + up_read(&zram->init_lock);
> + ret = len;
> +
> + return ret;
> +}
> +
> +static ssize_t writeback_batch_size_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + u32 val;
> + struct zram *zram = dev_to_zram(dev);
> +
> + down_read(&zram->init_lock);
> + val = zram->wb_batch_size;
> + up_read(&zram->init_lock);
> +
> + return sysfs_emit(buf, "%u\n", val);
> +}
> +
> static void reset_bdev(struct zram *zram)
> {
> if (!zram->backing_dev)
> @@ -779,10 +815,7 @@ static void release_wb_ctl(struct zram_wb_ctl *wb_ctl)
> kfree(wb_ctl);
> }
>
> -/* XXX: should be a per-device sysfs attr */
> -#define ZRAM_WB_REQ_CNT 32
> -
> -static struct zram_wb_ctl *init_wb_ctl(void)
> +static struct zram_wb_ctl *init_wb_ctl(struct zram *zram)
> {
> struct zram_wb_ctl *wb_ctl;
> int i;
> @@ -797,7 +830,7 @@ static struct zram_wb_ctl *init_wb_ctl(void)
> init_waitqueue_head(&wb_ctl->done_wait);
> spin_lock_init(&wb_ctl->done_lock);
>
> - for (i = 0; i < ZRAM_WB_REQ_CNT; i++) {
> + for (i = 0; i < zram->wb_batch_size; i++) {
> struct zram_wb_req *req;
>
> /*
> @@ -1197,7 +1230,7 @@ static ssize_t writeback_store(struct device *dev,
> goto release_init_lock;
> }
>
> - wb_ctl = init_wb_ctl();
> + wb_ctl = init_wb_ctl(zram);
> if (!wb_ctl) {
> ret = -ENOMEM;
> goto release_init_lock;
> @@ -2840,6 +2873,7 @@ static DEVICE_ATTR_RW(backing_dev);
> static DEVICE_ATTR_WO(writeback);
> static DEVICE_ATTR_RW(writeback_limit);
> static DEVICE_ATTR_RW(writeback_limit_enable);
> +static DEVICE_ATTR_RW(writeback_batch_size);
> #endif
> #ifdef CONFIG_ZRAM_MULTI_COMP
> static DEVICE_ATTR_RW(recomp_algorithm);
> @@ -2861,6 +2895,7 @@ static struct attribute *zram_disk_attrs[] = {
> &dev_attr_writeback.attr,
> &dev_attr_writeback_limit.attr,
> &dev_attr_writeback_limit_enable.attr,
> + &dev_attr_writeback_batch_size.attr,
> #endif
> &dev_attr_io_stat.attr,
> &dev_attr_mm_stat.attr,
> @@ -2922,6 +2957,7 @@ static int zram_add(void)
>
> init_rwsem(&zram->init_lock);
> #ifdef CONFIG_ZRAM_WRITEBACK
> + zram->wb_batch_size = 32;
> spin_lock_init(&zram->wb_limit_lock);
> #endif
>
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index 6cee93f9c0d0..1a647f42c1a4 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -129,6 +129,7 @@ struct zram {
> struct file *backing_dev;
> spinlock_t wb_limit_lock;
> bool wb_limit_enable;
> + u32 wb_batch_size;
> u64 bd_wb_limit;
> struct block_device *bdev;
> unsigned long *bitmap;
> --
> 2.52.0.rc1.455.g30608eb744-goog
>
On (25/11/20 10:57), Brian Geffon wrote:
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index 37c1416ac902..7904159e9226 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -588,6 +588,42 @@ static ssize_t writeback_limit_show(struct device *dev,
> > return sysfs_emit(buf, "%llu\n", val);
> > }
> >
> > +static ssize_t writeback_batch_size_store(struct device *dev,
> > + struct device_attribute *attr,
> > + const char *buf, size_t len)
> > +{
> > + struct zram *zram = dev_to_zram(dev);
> > + u32 val;
> > + ssize_t ret = -EINVAL;
> > +
> > + if (kstrtouint(buf, 10, &val))
> > + return ret;
> > +
> > + if (!val)
> > + val = 1;
>
> IMO a value of 0 for the batch size doesn't make sense, -EINVAL?
Ack.
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