The patch titled
Subject: dax: increase granularity of dax_clear_blocks() operations
has been added to the -mm tree. Its filename is
dax-increase-granularity-of-dax_clear_blocks-operations.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/dax-increase-granularity-of-dax_clear_blocks-operations.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/dax-increase-granularity-of-dax_clear_blocks-operations.patch
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From: Dan Williams <dan.j.williams@xxxxxxxxx>
Subject: 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@xxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxxx>
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/dax.c | 22 ++++++++--------------
1 file changed, 8 insertions(+), 14 deletions(-)
diff -puN fs/dax.c~dax-increase-granularity-of-dax_clear_blocks-operations fs/dax.c
--- a/fs/dax.c~dax-increase-granularity-of-dax_clear_blocks-operations
+++ a/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
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();
_
Patches currently in -mm which might be from dan.j.williams@xxxxxxxxx are
scatterlist-fix-sg_phys-masking.patch
pmem-dax-clean-up-clear_pmem.patch
dax-increase-granularity-of-dax_clear_blocks-operations.patch
dax-guarantee-page-aligned-results-from-bdev_direct_access.patch
dax-fix-lifetime-of-in-kernel-dax-mappings-with-dax_map_atomic.patch
dax-fix-lifetime-of-in-kernel-dax-mappings-with-dax_map_atomic-v3.patch
um-kill-pfn_t.patch
kvm-rename-pfn_t-to-kvm_pfn_t.patch
mm-dax-pmem-introduce-pfn_t.patch
mm-dax-pmem-introduce-pfn_t-v3.patch
mm-introduce-find_dev_pagemap.patch
x86-mm-introduce-vmem_altmap-to-augment-vmemmap_populate.patch
libnvdimm-pfn-pmem-allocate-memmap-array-in-persistent-memory.patch
avr32-convert-to-asm-generic-memory_modelh.patch
hugetlb-fix-compile-error-on-tile.patch
frv-fix-compiler-warning-from-definition-of-__pmd.patch
x86-mm-introduce-_page_devmap.patch
mm-dax-gpu-convert-vm_insert_mixed-to-pfn_t.patch
mm-dax-convert-vmf_insert_pfn_pmd-to-pfn_t.patch
list-introduce-list_del_poison.patch
libnvdimm-pmem-move-request_queue-allocation-earlier-in-probe.patch
mm-dax-pmem-introduce-getput_dev_pagemap-for-dax-gup.patch
mm-dax-dax-pmd-vs-thp-pmd-vs-hugetlbfs-pmd.patch
mm-x86-get_user_pages-for-dax-mappings.patch
dax-provide-diagnostics-for-pmd-mapping-failures.patch
dax-re-enable-dax-pmd-mappings.patch
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