NFS current abort and attempt at filename lookup in RCU mode.
This can have serious performance impact on a highly parallel load.
The "Makefile" below generates just such a load. On a 40-core
machine "make -j 40" is about 6 times as fast at "make -j 5"
when a local filesystem is used (e.g. XFS), but as much as half
as fast when NFS is used.
With this patch set, "make -j 40" is about 3 times as fast as
"make -j 5" on NFS, and "perf" data doesn't show spinlocks to be a big
problem any more.
This is a re-submission with a few small improvements of a patch set
posted in March. Since then I have recieved confirmation that it
definitely fixes the problem, when combined with a patch set which
enhances autofs4 in a similar way. So it has had quite a bit of
testing.
NeilBrown
The makefile. Run
make -f this-makefile NFS_PATH=/some/nfs/mounted/empty/directory
and an 'objs' directory will be created with lots of objects.
Use "make clean" before trying again.
---
# Options available from the command line
NUM_NFS_INCLUDES := 50
NUM_COMPILES := 200
NFS_PATH:=/import/dummySrc
# When adding includes, they will be of the form $(NFS_PATH)/x where
# x ranges from 1 to NUM_NFS_INCLUDES. Those directories are created
# automatically by the 'dirs' target.
SHELL:=bash
OBJ_DIR:=objs
ifeq ($(VERBOSE),1)
Q =
else
Q = @
endif
MY_INCLUDES := $(addprefix -I$(NFS_PATH)/, $(shell echo {1..$(NUM_NFS_INCLUDES)}))
INCLUDE_DIRS := $(addprefix $(NFS_PATH)/, $(shell echo {1..$(NUM_NFS_INCLUDES)}))
MY_OBJS := $(addsuffix _test.o, $(addprefix $(OBJ_DIR)/, $(shell echo {1..$(NUM_COMPILES)})))
build: dirs $(MY_OBJS)
dirs:
$(Q)mkdir -p $(INCLUDE_DIRS)
clean:
$(Q)rm -rf $(OBJ_DIR)
$(OBJ_DIR)/:
$(Q)/bin/mkdir $(OBJ_DIR)
$(MY_OBJS): test.cpp | $(OBJ_DIR)/
$(Q)gcc $(MY_INCLUDES) -c test.cpp -o $@
test.cpp:
$(Q)echo "#include <iostream>" > test.cpp
.PHONY: all build clean
---
NeilBrown (7):
NFS: nfs4_lookup_revalidate: only evaluate parent if it will be used.
NFS: prepare for RCU-walk support but pushing tests later in code.
sunrpc/auth: allow lockless (rcu) lookup of credential cache.
NFS: support RCU_WALK in nfs_permission()
NFS: teach nfs_neg_need_reval to understand LOOKUP_RCU
NFS: teach nfs_lookup_verify_inode to handle LOOKUP_RCU
NFS: allow lockless access to access_cache
fs/nfs/dir.c | 166 ++++++++++++++++++++++++++++++++++---------
fs/nfs/inode.c | 9 ++
include/linux/nfs_fs.h | 2 +
include/linux/sunrpc/auth.h | 2 +
net/sunrpc/auth.c | 17 ++++
net/sunrpc/auth_generic.c | 6 ++
net/sunrpc/auth_null.c | 2 +
7 files changed, 168 insertions(+), 36 deletions(-)
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