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 <roger.pau@xxxxxxxxxx>
---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: SeongJae Park <sjpark@xxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: linux-block@xxxxxxxxxxxxxxx
Cc: J. Roeleveld <joost@xxxxxxxxxxxx>
Cc: Jürgen Groß <jgross@xxxxxxxx>
---
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 <roger.pau@xxxxxxxxxx>
+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
