First of a number of files_lock scaability patches.
Here are the x86 numbers -
tiobench on a 4(8)-way (HT) P4 system on ramdisk :
(lockfree)
Test 2.6.10-vanilla Stdev 2.6.10-fd Stdev
-------------------------------------------------------------
Seqread 1400.8 11.52 1465.4 34.27
Randread 1594 8.86 2397.2 29.21
Seqwrite 242.72 3.47 238.46 6.53
Randwrite 445.74 9.15 446.4 9.75
The performance improvement is very significant.
We are getting killed by the cacheline bouncing of the files_struct
lock here. Writes on ramdisk (ext2) seems to vary just too
much to get any meaningful number.
Also, With Tridge's thread_perf test on a 4(8)-way (HT) P4 xeon system :
2.6.12-rc5-vanilla :
Running test 'readwrite' with 8 tasks
Threads 0.34 +/- 0.01 seconds
Processes 0.16 +/- 0.00 seconds
2.6.12-rc5-fd :
Running test 'readwrite' with 8 tasks
Threads 0.17 +/- 0.02 seconds
Processes 0.17 +/- 0.02 seconds
I repeated the measurements on ramfs (as opposed to ext2 on ramdisk in
the earlier measurement) and I got more consistent results from tiobench :
4(8) way xeon P4
-----------------
(lock-free)
Test 2.6.12-rc5 Stdev 2.6.12-rc5-fd Stdev
-------------------------------------------------------------
Seqread 1282 18.59 1343.6 26.37
Randread 1517 7 2415 34.27
Seqwrite 702.2 5.27 709.46 5.9
Randwrite 846.86 15.15 919.68 21.4
4-way ppc64
------------
(lock-free)
Test 2.6.12-rc5 Stdev 2.6.12-rc5-fd Stdev
-------------------------------------------------------------
Seqread 1549 91.16 1569.6 47.2
Randread 1473.6 25.11 1585.4 69.99
Seqwrite 1096.8 20.03 1136 29.61
Randwrite 1189.6 4.04 1275.2 32.96
Also running Tridge's thread_perf test on ppc64 :
2.6.12-rc5-vanilla
--------------------
Running test 'readwrite' with 4 tasks
Threads 0.20 +/- 0.02 seconds
Processes 0.16 +/- 0.01 seconds
2.6.12-rc5-fd
--------------------
Running test 'readwrite' with 4 tasks
Threads 0.18 +/- 0.04 seconds
Processes 0.16 +/- 0.01 seconds
The benefits are huge (upto ~60%) in some cases on x86 primarily
due to the atomic operations during acquisition of ->file_lock
and cache line bouncing in fast path. ppc64 benefits are modest
due to LL/SC based locking, but still statistically significant.
This patch:
RCU head initilizer no longer needs the head varible name since we don't use
list.h lists anymore.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The synchronize_kernel() primitive is used for quite a few different purposes:
waiting for RCU readers, waiting for NMIs, waiting for interrupts, and so on.
This makes RCU code harder to read, since synchronize_kernel() might or might
not have matching rcu_read_lock()s. This patch creates a new
synchronize_rcu() that is to be used for RCU readers and a new
synchronize_sched() that is used for the rest. These two new primitives
currently have the same implementation, but this is might well change with
additional real-time support. Both new primitives are GPL-only, the old
primitive is deprecated.
Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Dipankar Sarma
Paul E. McKenney
Linus Torvalds