Re: [PATCH 1/2] xen/blkback: turn the cache purge LRU interval into a parameter

2020-10-15 Thread SeongJae Park 
On Thu, 15 Oct 2020 16:24:15 +0200 Roger Pau Monne  wrote:

> Assume that reads and writes to the variable will be atomic. The worse
> that could happen is that one of the LRU intervals is not calculated
> properly if a partially written value is read, but that would only be
> a transient issue.
> 
> Signed-off-by: Roger Pau Monné 
> ---
> Cc: Konrad Rzeszutek Wilk 
> Cc: Jens Axboe 
> Cc: Boris Ostrovsky 
> Cc: SeongJae Park 
> Cc: xen-de...@lists.xenproject.org
> Cc: linux-bl...@vger.kernel.org
> Cc: J. Roeleveld 
> Cc: Jürgen Groß 
> ---
>  Documentation/ABI/testing/sysfs-driver-xen-blkback | 10 ++
>  drivers/block/xen-blkback/blkback.c|  9 ++---
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback 
> b/Documentation/ABI/testing/sysfs-driver-xen-blkback
> index ecb7942ff146..776f25d335ca 100644
> --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback
> +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback
> @@ -35,3 +35,13 @@ Description:
>  controls the duration in milliseconds that blkback will not
>  cache any page not backed by a grant mapping.
>  The default is 10ms.
> +
> +What:   /sys/module/xen_blkback/parameters/lru_internval
> +Date:   October 2020
> +KernelVersion:  5.10
> +Contact:Roger Pau Monné 
> +Description:
> +The LRU mechanism to clean the lists of persistent grants 
> needs
> +to be executed periodically. This parameter controls the time
> +interval between consecutive executions of the purge 
> mechanism
> +is set in ms.

I think noticing the default value (100ms) here would be better.


Thanks,
SeongJae Park

Re: [PATCH 1/2] xen/blkback: turn the cache purge LRU interval into a parameter

2020-10-15 Thread Jürgen Groß 

On 15.10.20 16:24, Roger Pau Monne wrote:

Assume that reads and writes to the variable will be atomic. The worse
that could happen is that one of the LRU intervals is not calculated
properly if a partially written value is read, but that would only be
a transient issue.

Signed-off-by: Roger Pau Monné 
---
Cc: Konrad Rzeszutek Wilk 
Cc: Jens Axboe 
Cc: Boris Ostrovsky 
Cc: SeongJae Park 
Cc: xen-de...@lists.xenproject.org
Cc: linux-bl...@vger.kernel.org
Cc: J. Roeleveld 
Cc: Jürgen Groß 
---
  Documentation/ABI/testing/sysfs-driver-xen-blkback | 10 ++
  drivers/block/xen-blkback/blkback.c|  9 ++---
  2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback 
b/Documentation/ABI/testing/sysfs-driver-xen-blkback
index ecb7942ff146..776f25d335ca 100644
--- a/Documentation/ABI/testing/sysfs-driver-xen-blkback
+++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback
@@ -35,3 +35,13 @@ Description:
  controls the duration in milliseconds that blkback will not
  cache any page not backed by a grant mapping.
  The default is 10ms.
+
+What:   /sys/module/xen_blkback/parameters/lru_internval


s/lru_internval/lru_interval/


+Date:   October 2020
+KernelVersion:  5.10
+Contact:Roger Pau Monné 
+Description:
+The LRU mechanism to clean the lists of persistent grants needs
+to be executed periodically. This parameter controls the time
+interval between consecutive executions of the purge mechanism
+is set in ms.
diff --git a/drivers/block/xen-blkback/blkback.c 
b/drivers/block/xen-blkback/blkback.c
index adfc9352351d..6ad9b76fdb2b 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -117,7 +117,10 @@ MODULE_PARM_DESC(max_ring_page_order, "Maximum order of 
pages to be used for the
   * be executed periodically. The time interval between consecutive executions
   * of the purge mechanism is set in ms.
   */
-#define LRU_INTERVAL 100
+static unsigned int lru_interval = 100;
+module_param_named(lru_interval, lru_interval, uint, 0644);
+MODULE_PARM_DESC(lru_internval,


s/lru_internval/lru_interval/


+"Time interval between consecutive executions of the cache purge 
mechanism (in ms)");
  
  /*

   * When the persistent grants list is full we will remove unused grants
@@ -620,7 +623,7 @@ int xen_blkif_schedule(void *arg)
if (unlikely(vbd->size != vbd_sz(vbd)))
xen_vbd_resize(blkif);
  
-		timeout = msecs_to_jiffies(LRU_INTERVAL);

+   timeout = msecs_to_jiffies(lru_interval);
  
  		timeout = wait_event_interruptible_timeout(

ring->wq,
@@ -650,7 +653,7 @@ int xen_blkif_schedule(void *arg)
if (blkif->vbd.feature_gnt_persistent &&
time_after(jiffies, ring->next_lru)) {
purge_persistent_gnt(ring);
-   ring->next_lru = jiffies + 
msecs_to_jiffies(LRU_INTERVAL);
+   ring->next_lru = jiffies + 
msecs_to_jiffies(lru_interval);
}
  
  		/* Shrink the free pages pool if it is too large. */





Juergen

[PATCH 1/2] xen/blkback: turn the cache purge LRU interval into a parameter

2020-10-15 Thread Roger Pau Monne 
Assume that reads and writes to the variable will be atomic. The worse
that could happen is that one of the LRU intervals is not calculated
properly if a partially written value is read, but that would only be
a transient issue.

Signed-off-by: Roger Pau Monné 
---
Cc: Konrad Rzeszutek Wilk 
Cc: Jens Axboe 
Cc: Boris Ostrovsky 
Cc: SeongJae Park 
Cc: xen-de...@lists.xenproject.org
Cc: linux-bl...@vger.kernel.org
Cc: J. Roeleveld 
Cc: Jürgen Groß 
---
 Documentation/ABI/testing/sysfs-driver-xen-blkback | 10 ++
 drivers/block/xen-blkback/blkback.c|  9 ++---
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback 
b/Documentation/ABI/testing/sysfs-driver-xen-blkback
index ecb7942ff146..776f25d335ca 100644
--- a/Documentation/ABI/testing/sysfs-driver-xen-blkback
+++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback
@@ -35,3 +35,13 @@ Description:
 controls the duration in milliseconds that blkback will not
 cache any page not backed by a grant mapping.
 The default is 10ms.
+
+What:   /sys/module/xen_blkback/parameters/lru_internval
+Date:   October 2020
+KernelVersion:  5.10
+Contact:Roger Pau Monné 
+Description:
+The LRU mechanism to clean the lists of persistent grants needs
+to be executed periodically. This parameter controls the time
+interval between consecutive executions of the purge mechanism
+is set in ms.
diff --git a/drivers/block/xen-blkback/blkback.c 
b/drivers/block/xen-blkback/blkback.c
index adfc9352351d..6ad9b76fdb2b 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -117,7 +117,10 @@ MODULE_PARM_DESC(max_ring_page_order, "Maximum order of 
pages to be used for the
  * be executed periodically. The time interval between consecutive executions
  * of the purge mechanism is set in ms.
  */
-#define LRU_INTERVAL 100
+static unsigned int lru_interval = 100;
+module_param_named(lru_interval, lru_interval, uint, 0644);
+MODULE_PARM_DESC(lru_internval,
+"Time interval between consecutive executions of the cache 
purge mechanism (in ms)");
 
 /*
  * When the persistent grants list is full we will remove unused grants
@@ -620,7 +623,7 @@ int xen_blkif_schedule(void *arg)
if (unlikely(vbd->size != vbd_sz(vbd)))
xen_vbd_resize(blkif);
 
-   timeout = msecs_to_jiffies(LRU_INTERVAL);
+   timeout = msecs_to_jiffies(lru_interval);
 
timeout = wait_event_interruptible_timeout(
ring->wq,
@@ -650,7 +653,7 @@ int xen_blkif_schedule(void *arg)
if (blkif->vbd.feature_gnt_persistent &&
time_after(jiffies, ring->next_lru)) {
purge_persistent_gnt(ring);
-   ring->next_lru = jiffies + 
msecs_to_jiffies(LRU_INTERVAL);
+   ring->next_lru = jiffies + 
msecs_to_jiffies(lru_interval);
}
 
/* Shrink the free pages pool if it is too large. */
-- 
2.28.0