When dm-writecache is used with SSD as a cache device, it would submit a
separate bio for each written block. The I/Os would be merged by the disk
scheduler, but this merging degrades performance.
Improve dm-writecache performance by submitting larger bios - this is
possible as long as there is consecutive free space on the cache
device.
Benchmark (arm64 with 64k page size, using /dev/ram0 as a cache device):
fio --bs=512k --iodepth=32 --size=400M --direct=1 \
--filename=/dev/mapper/cache --rw=randwrite --numjobs=1 --name=test
block old new
size MiB/s MiB/s
---------------------
512 181 700
1k 347 1256
2k 644 2020
4k 1183 2759
8k 1852 3333
16k 2469 3509
32k 2974 3670
64k 3404 3810
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
When committing state, the function writecache_flush does the following:
1. write metadata (writecache_commit_flushed)
2. flush disk cache (writecache_commit_flushed)
3. wait for data writes to complete (writecache_wait_for_ios)
4. increase superblock seq_count
5. write the superblock
6. flush disk cache
It may happen that at step 3, when we wait for some write to finish, the
disk may report the write as finished, but the write only hit the disk
cache and it is not yet stored in persistent storage. At step 5 we write
the superblock - it may happen that the superblock is written before the
write that we waited for in step 3. If the machine crashes, it may result
in incorrect data being returned after reboot.
In order to fix the bug, we must swap steps 2 and 3 in the above sequence,
so that we first wait for writes to complete and then flush the disk
cache.
Fixes: 48debafe4f ("dm: add writecache target")
Cc: stable@vger.kernel.org # 4.18+
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The array bio_in_progress[2] only have chance to be increased and
decreased with ssd mode. For pmem mode, they are not involved at all.
So skip writecache_wait_for_ios in writecache_flush for pmem.
Suggested-by: Doris Yu <tyu1@lenovo.com>
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
During the process of writeback, the blocks, which have been placed in wbl.list
for writeback soon, are partially ordered for the contiguous ones.
When writeback_all has been set, for most cases, also by default, there will be
a lot of blocks in pmem need to writeback at the same time.
For this case, we could optimize the performance by sorting all blocks in
wbl.list. writecache_writeback doesn't need to get blocks from the tail of
wc->lru, whereas from the first rb_node from the rb_tree.
The benefit is that, writecache_writeback doesn't need to have any cost to sort
the blocks, because of all blocks are incremental originally in rb_tree.
There will be a writecache_flush when writeback_all begins to work, that will
eliminate duplicate blocks in cache by committed/uncommitted.
Testing platform: Thinksystem SR630 with persistent memory.
The cache comes from pmem, which has 1006MB size. The origin device is HDD, 2GB
of which for using.
Testing steps:
1) dmsetup create mycache --table '0 4194304 writecache p /dev/sdb1 /dev/pmem4 4096 0'
2) fio -filename=/dev/mapper/mycache -direct=1 -iodepth=20 -rw=randwrite
-ioengine=libaio -bs=4k -loops=1 -size=2g -group_reporting -name=mytest1
3) time dmsetup message /dev/mapper/mycache 0 flush
Here is the results below,
With the patch:
# fio -filename=/dev/mapper/mycache -direct=1 -iodepth=20 -rw=randwrite
-ioengine=libaio -bs=4k -loops=1 -size=2g -group_reporting -name=mytest1
iops : min= 1582, max=199470, avg=5305.94, stdev=21273.44, samples=197
# time dmsetup message /dev/mapper/mycache 0 flush
real 0m44.020s
user 0m0.002s
sys 0m0.003s
Without the patch:
# fio -filename=/dev/mapper/mycache -direct=1 -iodepth=20 -rw=randwrite
-ioengine=libaio -bs=4k -loops=1 -size=2g -group_reporting -name=mytest1
iops : min= 1202, max=197650, avg=4968.67, stdev=20480.17, samples=211
# time dmsetup message /dev/mapper/mycache 0 flush
real 1m39.221s
user 0m0.001s
sys 0m0.003s
I also have checked the data accuracy with this patch by making EXT4 filesystem
on mycache, then mount it for checking md5 of files on that.
The test result is positive, with this patch it could save more than half of time
when writeback_all.
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
In function writecache_writeback, entries g and f has same original
sector only happens at entry f has been committed, but entry g has
NOT yet.
The probability of this happening is very low in the following
256 blocks at most of entry e.
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The stucture member pointer page in writeback_struct never has been
used actually. Remove it.
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This is a small optimization in writecache_find_entry().
If we go past the condition "if (unlikely(!node))", we can be certain that
there is no entry in the tree that has the block equal to the "block"
variable.
Consequently, we can return the next entry directly, we don't need to go
to the second part of the function that finds the entry with lowest or
highest seq number that matches the "block" variable.
Also, add some whitespace and cleanup needless braces.
Suggested-by: Huaisheng Ye <yehs1@lenovo.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The stucture member page_offset in writeback_struct never has been
used actually. Remove it.
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
In functions writecache_discard() and writecache_find_entry() there is a
high probablity that the pointer of structure rb_node won't equal NULL.
Add unlikely for the pointer node NULL.
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
bio is already available so there is no need to access it in terms of
the wb pointer.
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The workqueue's name should be "writecache-writeback" instead of
"writecache-writeabck".
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The error msg should be "flush thread" instead of "endio thread"
for writecache_flush_thread.
Signed-off-by: Shenghui Wang <shhuiw@foxmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This dead branch was missed during review. It only makes memory_entry()
more inefficient due to needless call to is_power_of_2(), etc.
Reported-by: shenghui <shhuiw@foxmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Collection of misc libnvdimm patches for 4.19 submission
* Adding support to read locked nvdimm capacity.
* Change test code to make DSM failure code injection an override.
* Add support for calculate maximum contiguous area for namespace.
* Add support for queueing a short ARS when there is on going ARS for
nvdimm.
* Allow NULL to be passed in to ->direct_access() for kaddr and
pfn params.
* Improve smart injection support for nvdimm emulation testing.
* Fix test code that supports for emulating controller temperature.
* Fix hang on error before devm_memremap_pages()
* Fix a bug that causes user memory corruption when data returned
to user for ars_status.
* Maintainer updates for Ross Zwisler emails and adding Jan Kara to fsdax.
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Merge tag 'libnvdimm-for-4.19_misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/nvdimm/nvdimm
Pull libnvdimm updates from Dave Jiang:
"Collection of misc libnvdimm patches for 4.19 submission:
- Adding support to read locked nvdimm capacity.
- Change test code to make DSM failure code injection an override.
- Add support for calculate maximum contiguous area for namespace.
- Add support for queueing a short ARS when there is on going ARS for
nvdimm.
- Allow NULL to be passed in to ->direct_access() for kaddr and pfn
params.
- Improve smart injection support for nvdimm emulation testing.
- Fix test code that supports for emulating controller temperature.
- Fix hang on error before devm_memremap_pages()
- Fix a bug that causes user memory corruption when data returned to
user for ars_status.
- Maintainer updates for Ross Zwisler emails and adding Jan Kara to
fsdax"
* tag 'libnvdimm-for-4.19_misc' of gitolite.kernel.org:pub/scm/linux/kernel/git/nvdimm/nvdimm:
libnvdimm: fix ars_status output length calculation
device-dax: avoid hang on error before devm_memremap_pages()
tools/testing/nvdimm: improve emulation of smart injection
filesystem-dax: Do not request kaddr and pfn when not required
md/dm-writecache: Don't request pointer dummy_addr when not required
dax/super: Do not request a pointer kaddr when not required
tools/testing/nvdimm: kaddr and pfn can be NULL to ->direct_access()
s390, dcssblk: kaddr and pfn can be NULL to ->direct_access()
libnvdimm, pmem: kaddr and pfn can be NULL to ->direct_access()
acpi/nfit: queue issuing of ars when an uc error notification comes in
libnvdimm: Export max available extent
libnvdimm: Use max contiguous area for namespace size
MAINTAINERS: Add Jan Kara for filesystem DAX
MAINTAINERS: update Ross Zwisler's email address
tools/testing/nvdimm: Fix support for emulating controller temperature
tools/testing/nvdimm: Make DSM failure code injection an override
acpi, nfit: Prefer _DSM over _LSR for namespace label reads
libnvdimm: Introduce locked DIMM capacity support
wc->dirty_bitmap_size is in bytes so must multiply it by 8, not by
BITS_PER_LONG, to get number of bitmap_bits.
Fixes crash in find_next_bit() that was reported:
https://bugzilla.kernel.org/show_bug.cgi?id=200819
Reported-by: edo.rus@gmail.com
Fixes: 48debafe4f ("dm: add writecache target")
Cc: stable@vger.kernel.org # 4.18
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Function persistent_memory_claim doesn't need to get local pointer
dummy_addr from direct_access. Using NULL instead of having to pass
in a useless local pointer that caller then just throw away.
Suggested-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Huaisheng Ye <yehs1@lenovo.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Fixes: d284f8248c ("dm writecache: support optional offset for start of device")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add an optional parameter "start_sector" to allow the start of the
device to be offset by the specified number of 512-byte sectors. The
sectors below this offset are not used by the writecache device and are
left to be used for disk labels and/or userspace metadata (e.g. lvm).
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This adjusts the allocator calls to use the 2-factor argument style, as
already done treewide for better defense against allocator overflows.
Signed-off-by: Kees Cook <keescook@chromium.org>
[snitzer: tweaked code to leave assignment in a test alone]
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The writecache target caches writes on persistent memory or SSD.
It is intended for databases or other programs that need extremely low
commit latency.
The writecache target doesn't cache reads because reads are supposed to
be cached in page cache in normal RAM.
If persistent memory isn't available this target can still be used in
SSD mode.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com> # fix missing goto
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> # fix compilation issue with !DAX
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> # use msecs_to_jiffies
Acked-by: Dan Williams <dan.j.williams@intel.com> # reworks to unify ARM and x86 flushing
Signed-off-by: Mike Snitzer <msnitzer@redhat.com>
