Hi all,
This is my fifth try to implement the second step of extent status tree.
The patch set can be divided into the following parts.
Patch 1/10
This patch refines the extent status tree
Patch 2/10-6/10
These patches try to track all extent status in extent status tree and
make it as a extent cache. In extent_status structure bit field is removed
because we get some warnings from 'sparse'. Now es_pblk and es_status are
manipulated by ext4_es_*_pblock and ext4_es_*_status directly. Currently
when an unwritten extent is allocated, we never know it from map->m_flags
because ext4_ext_map_blocks doesn't return EXT4_MAP_UNWRITTEN flag. A
patch fixes it and we can determine the extent status according to m_flags.
According to Jan's feedback, we put the hole into extent cache to avoid
to access extent tree in disk as far as possible. Here if the whole file
is a hole, this hole will not be cached in extent status tree because it
is always splitted immediately. Meanwhile the hole will not be cached
when ext4_da_map_blocks looks up a block mapping because this hole will be
as a delayed extent later.
Patch 7/10-8/10
This two patches try to reclaim memory from extent status tree when we
are under a high memeory pressure.
Patch 9/10-10/10
Thses patches are picked up again from 1st version because I aware that
they could remove a bogus wait in ext4_ind_direct_IO when dioread_nolock
is enabled. After applied them, the latency of dio read can be reduced.
I measure it using fio and the result shows as below.
config file
-----------
[global]
ioengine=psync
direct=1
bs=4k
thread
group_reporting
directory=/mnt/sda1/
filename=testfile
filesize=10g
size=10g
runtime=120
iodepth=16
[fio]
rw=randrw
numjobs=4
result
------
w/ bogus wait
read : io=1508.1MB, bw=12876KB/s, iops=3218 , runt=120001msec
clat (usec): min=128 , max=268738 , avg=718.62, stdev=3703.97
lat (usec): min=128 , max=268739 , avg=718.78, stdev=3703.97
write: io=1505.2MB, bw=12843KB/s, iops=3210 , runt=120001msec
clat (usec): min=47 , max=991727 , avg=520.94, stdev=3451.63
lat (usec): min=47 , max=991727 , avg=521.31, stdev=3451.63
w/o bogus wait
read : io=1576.4MB, bw=13451KB/s, iops=3362 , runt=120001msec
clat (usec): min=128 , max=283906 , avg=685.88, stdev=2762.64
lat (usec): min=128 , max=283907 , avg=686.05, stdev=2762.64
write: io=1577.9MB, bw=13458KB/s, iops=3364 , runt=120001msec
clat (usec): min=48 , max=977942 , avg=498.97, stdev=3093.08
lat (usec): min=48 , max=977943 , avg=499.33, stdev=3093.08
>From the result we can see that the avg. of latency could be reduced a little.
changelog:
v5 <- v4:
- drop a patch that removes EXT4_MAP_FROM_CLUSTER flag
(I will revise it in the patch set of get_block_t refinement)
- fold original patch 3/9 into patch 4/9
- manipulate es_pblk and es_status directly
(bit field is removed because it causes some warnings from 'sparse')
- let ext4_ext_map_blocks return EXT4_MAP_UNWRITTEN flag
- rename ext4_es_find_extent with ext4_es_find_delayed_extent
- add hole status and put hole into extent status tree as a cache
- convert unwritten extents from extent status tree in ext4_ext_direct_IO
and end_io callback
- remove a bogus wait in ext4_ind_direct_IO when dioread_nolock is enabled
v4 <- v3:
- register a normal shrinker to reclaim extent from extent status tree
v3 <- v2:
- use prune_super() to reclaim extents from extent status tree
- stashed es_status into es_pblk
- remove single extent cache
- rebase against 3.8-rc4
v2 <- v1:
- drop patches that try to improve unwritten extent conversion
- remove EXT4_MAP_FROM_CLUSTER flag
- add tracepoint for ext4_es_lookup_extent()
- drop a patch, which tries to fix a warning when bigalloc and delalloc
are enabled
- add a shrinker to reclaim memory from extent status tree
- rebase against 3.8-rc2
v4: http://lwn.net/Articles/536037/
v3: http://lwn.net/Articles/533730/
v2: http://lwn.net/Articles/532446/
v1: http://lwn.net/Articles/531065/
As always, any comments or feedbacks are welcome.
FWIW, when I try to implement patch 3/10, I realize that get_block_t and
*_map_blocks functions need to be refactored because in ext4 we already
have six get_block_t functions
- ext4_get_block
- ext4_get_block_write
- ext4_get_block_write_nolock
- noalloc_get_block_write
- ext4_da_get_block_prep
- _ext4_get_block
and four *_map_blocks
- ext4_map_blocks
- ext4_da_map_blocks
- ext4_ext_map_blocks
- ext4_ind_map_blocks
So I am planning to refine them. First I will try to split ext4_map_blocks
into two parts, e.g. ext4_map_blocks_read and ext4_map_blocks_write, and
then try other cleanups and improvmentes.
Thanks,
- Zheng
Zheng Liu (10):
ext4: refine extent status tree
ext4: add physical block and status member into extent status tree
ext4: let ext4_ext_map_blocks return EXT4_MAP_UNWRITTEN flag
ext4: track all extent status in extent status tree
ext4: lookup block mapping in extent status tree
ext4: remove single extent cache
ext4: adjust some functions for reclaiming extents from extent status
tree
ext4: reclaim extents from extent status tree
ext4: convert unwritten extents from extent status tree in end_io
ext4: remove bogus wait for unwritten extents in ext4_ind_direct_IO
fs/ext4/ext4.h | 21 +-
fs/ext4/ext4_extents.h | 6 -
fs/ext4/extents.c | 211 ++++--------
fs/ext4/extents_status.c | 779 +++++++++++++++++++++++++++++++++++---------
fs/ext4/extents_status.h | 84 ++++-
fs/ext4/file.c | 16 +-
fs/ext4/indirect.c | 5 -
fs/ext4/inode.c | 148 +++++++--
fs/ext4/move_extent.c | 3 -
fs/ext4/page-io.c | 8 +-
fs/ext4/super.c | 8 +-
include/trace/events/ext4.h | 207 ++++++++++--
12 files changed, 1075 insertions(+), 421 deletions(-)
--
1.7.12.rc2.18.g61b472e
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