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dax: increase granularity of dax_clear_blocks() operations 

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.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jan Kara <jack@suse.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Williams 2016-01-15 16:55:53 -08:00 committed by Linus Torvalds
parent 52db400fcd
commit 0e749e5424
1 changed files with 8 additions and 14 deletions
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22
fs/dax.c
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@ -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();