dax_clear_blocks is currently performing a cond_resched() after every
PAGE_SIZE memset. We need not check so frequently, for example md-raid
only calls cond_resched() at stripe granularity. Also, in preparation
for introducing a dax_map_atomic() operation that temporarily pins a dax
mapping move the call to cond_resched() to the outer loop.
The worst case latency between calls to cond_resched() after this change
is 500us the average latency is 133us. This is up from a 10us max and
4us average.
Reviewed-by: Jan Kara <jack@xxxxxxxx>
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
fs/dax.c | 22 ++++++++--------------
1 file changed, 8 insertions(+), 14 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 19492cc65a30..11721c0fc127 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -28,6 +28,7 @@
#include <linux/sched.h>
#include <linux/uio.h>
#include <linux/vmstat.h>
+#include <linux/sizes.h>
/*
* dax_clear_blocks() is called from within transaction context from XFS,
@@ -43,24 +44,17 @@ int dax_clear_blocks(struct inode *inode, sector_t block, long size)
do {
void __pmem *addr;
unsigned long pfn;
- long count;
+ long count, sz;
count = bdev_direct_access(bdev, sector, &addr, &pfn, size);
if (count < 0)
return count;
- BUG_ON(size < count);
- while (count > 0) {
- unsigned pgsz = PAGE_SIZE - offset_in_page(addr);
- if (pgsz > count)
- pgsz = count;
- clear_pmem(addr, pgsz);
- addr += pgsz;
- size -= pgsz;
- count -= pgsz;
- BUG_ON(pgsz & 511);
- sector += pgsz / 512;
- cond_resched();
- }
+ sz = min_t(long, count, SZ_128K);
+ clear_pmem(addr, sz);
+ size -= sz;
+ BUG_ON(sz & 511);
+ sector += sz / 512;
+ cond_resched();
} while (size);
wmb_pmem();
--
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