based by vmalloc()'ed memory. I now alloc a slab which is
roughly 32*spl_obj_size and in this block of memory I place
the slab descriptor, slab object descriptors, and objects
themselves. This greatly reduces vmalloc lock contention.
Still some minor cleanup remains and fine tuning but
it's working pretty well.
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well for the expected workloads. Improvement in this commit include:
- Added DEBUG_KMEM_TRACKING #define which can optionally be set
when DEBUG_KMEM is defined to do per allocation tracking. This
allows us to get all the lightweight kmem debugging enabled by
default which is pretty light weight, and only when looking
for a memory leak we can briefly enable the per alloc tracking.
- Added set_normalized_timespec() in to SPL to simply using
the timespec() primatives from within a module.
- Added per-spinlock cycle counters to the slab in an attempt
to run down a lock contention issue. The contended lock
was in vmalloc() but I'm going to leave the cycle counters
in place for a little while until I'm convinced there arn't
other locking improvement possible in the slab.
- Added a proc interface to the slab to export per slab
cache statistics to /proc/spl/kmem/slab for analysis.
- Reworked spl_slab_alloc() function to allocate from kmem for
small allocation and vmem for large allocations. This improved
things considerably but futher work is needed.
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when repopulating it. Plus I fixed a few more suble races in
that part of the code which were catching me. Finally I fixed
a small race in kmem_test8.
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factor of 10x improvement on SMP system due to reduced lock contention.
This may put me in the ballpark of what is needed. We can still further
improve things on NUMA systems by creating an additional L3 cache per
memory node instead of the current global pool. With luck this won't
be needed. I should also take another look at the locking now that
everything is working. There's a good chance I can tighten it up a
little bit and improve things a little more.
kmem_lock: time (sec) slabs objs hash
kmem_lock: tot/max/calc tot/max/calc size/depth
kmem_lock: 0.000999926 6/6/1 192/192/32 32768/0
kmem_lock: 0.000999926 4/4/2 128/128/64 32768/0
kmem_lock: 0.000999926 4/4/4 128/128/128 32768/0
kmem_lock: 0.000999926 4/4/8 128/128/256 32768/0
kmem_lock: 0.000999926 4/4/16 128/128/512 32768/0
kmem_lock: 0.000999926 4/4/32 128/128/1024 32768/0
kmem_lock: 0.000999926 4/4/64 128/128/2048 32768/0
kmem_lock: 0.000999926 8/8/128 256/256/4096 32768/0
kmem_lock: 0.003999704 24/23/256 768/736/8192 32768/1
kmem_lock: 0.012999038 44/41/512 1408/1312/16384 32768/1
kmem_lock: 0.051996153 96/93/1024 3072/2976/32768 32768/2
kmem_lock: 0.181986536 187/184/2048 5984/5888/65536 32768/3
kmem_lock: 0.655951469 342/339/4096 10944/10848/131072 32768/4
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to be overly clever and the context switch when the semaphore was busy
was destroying performance. Converting to a simple spin lock bough me
a factor of 50 or so. That said it's still not good enough. Tests
show bad performance and we are still CPU bound. The logical fix is
I need to implement per-cpu hot caches to minimize the SMP contention.
Linux and Solaris both have this, I was hoping to do without but it
looks like that's not to be.
kmem_lock: time (sec) slabs objs hash
kmem_lock: tot/max/calc tot/max/calc size/depth
kmem_lock: 0.022000000 7/6/64 224/177/2048 32768/1
kmem_lock: 0.039000000 13/13/128 416/404/4096 32768/1
kmem_lock: 0.079000000 23/21/256 736/672/8192 32768/1
kmem_lock: 0.158000000 48/47/512 1536/1504/16384 32768/1
kmem_lock: 0.345000000 105/105/1024 3360/3358/32768 32768/2
kmem_lock: 0.760000000 202/200/2048 6464/6400/65536 32768/3
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longer be based on the linux slab but to be its own complete
implementation. The new slab behaves much more like the
Solaris slab than the Linux slab.
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1) Ensure mutex_init() never fails in the case of ENOMEM by retrying
forever. I don't think I've ever seen this happen but it was clear
after code inspection that if it did we would immediately crash.
2) Enable full debugging in check.sh for sanity tests. Might as well
get as much debug as we can in the case of a failure.
3) Reworked list of kmem caches tracked by SPL in to a hash with the
key based on the address of the kmem_cache_t. This should speed
up the constructor/destructor/shrinker lookup needed now for newer
kernel which removed the destructor support.
4) Updated kmem_cache_create to handle the case where CONFIG_SLUB
is defined. The slub would occasionally merge slab caches which
resulted in non-unique keys for our hash lookup in 3). To fix this
we detect if the slub is enabled and then set the needed flag
to prevent this merging from ever occuring.
5) New kernels removed the proc_dir_entry pointer from items
registered by sysctl. This means we can no long be sneaky and
manually insert things in to the sysctl tree simply by walking
the proc tree. So I'm forced to create a seperate tree for
all the things I can't easily support via sysctl interface.
I don't like it but it will do for now.
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working on this branch for the next few days I suggested you work
off of the 0.3.1 tag. The following changes are fairly extensive
and are designed to make the SPL compatible with all kernels in
the range of 2.6.18-2.6.25. There were 13 relevant API changes
between these releases and I have added the needed autoconf tests
to check for them. However, this has not all been tested extensively.
I'll sort of the breakage on Fedora Core 9 and RHEL5 this week.
SPL_AC_TYPE_UINTPTR_T
SPL_AC_TYPE_KMEM_CACHE_T
SPL_AC_KMEM_CACHE_DESTROY_INT
SPL_AC_ATOMIC_PANIC_NOTIFIER
SPL_AC_3ARGS_INIT_WORK
SPL_AC_2ARGS_REGISTER_SYSCTL
SPL_AC_KMEM_CACHE_T
SPL_AC_KMEM_CACHE_CREATE_DTOR
SPL_AC_3ARG_KMEM_CACHE_CREATE_CTOR
SPL_AC_SET_SHRINKER
SPL_AC_PATH_IN_NAMEIDATA
SPL_AC_TASK_CURR
SPL_AC_CTL_UNNUMBERED
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compiled out when doing performance runs.
- Bite the bullet and fully autoconfize the debug options in the configure
time parameters. By default all the debug support is disable in the core
SPL build, but available to modules which enable it when building against
the SPL. To enable particular SPL debug support use the follow configure
options:
--enable-debug Internal ASSERTs
--enable-debug-kmem Detailed memory accounting
--enable-debug-mutex Detailed mutex tracking
--enable-debug_kstat Kstat info exported to /proc
--enable-debug-callb Additional callb debug
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other primitive implementations. Additionally ensure that GFP_ATOMIC
is use for allocations when in interrupt context.
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may not fail. To get this behavior I'd added a retry to the shim layer
even though it is abusive to the VM, at least it should prevent the crash.
Additionally I added a proc counter so I can easily check how often this
is happening. It should be fairly rare, but likely will get worse and
worse the longer the machine has been up.
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not to support a few flags (we assert if they are used), and I
did not add the libkstat interface and instead exported everything
to proc for easy access.
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- Ensure the mutex_stats_sem and mutex_stats_list are initialized
- Only spin if you have to in mutex_init
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- Detailed kmem memory allocation tracking. We can now get on
spl module unload a list of all memory allocations which were
not free'd and where the original alloc was. E.g.
SPL: 15554:632:(spl-kmem.c:442:kmem_fini()) kmem leaked 90/319332 bytes
SPL: 15554:648:(spl-kmem.c:451:kmem_fini()) address size data func:line
SPL: 15554:648:(spl-kmem.c:457:kmem_fini()) ffff8100734b68b8 32 0100000001005a5a __spl_mutex_init:70
SPL: 15554:648:(spl-kmem.c:457:kmem_fini()) ffff8100734b6148 13 &tl->tl_lock __spl_mutex_init:74
SPL: 15554:648:(spl-kmem.c:457:kmem_fini()) ffff81007ac43730 32 0100000001005a5a __spl_mutex_init:70
SPL: 15554:648:(spl-kmem.c:457:kmem_fini()) ffff81007ac437d8 13 &tl->tl_lock __spl_mutex_init:74
- Shift to using rwsems in kmem implmentation, to simply locking and
improve concurency.
- Shift to using rwsems in mutex implementation, additionally ensure we
never sleep in the init function if non-zero preempt_count or
interrupts are disabled as can happen in a slab cache ctor/dtor.
- Other minor formating fixes and such.
TODO:
- Finish the vmem memory allocation tracking
- Vet all other SPL primatives for potential sleeping during *_init. I
suspect the rwlock implemenation does this and should be fixes just
like the mutex implemenation.
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crashes but it's not clear to me yet if these are a problem with
the mutex implementation or ZFSs usage of it.
Minor taskq fixes to add new tasks to the end of the pending list.
Minor enhansements to the debug infrastructure.
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configurable number of threads like the Solaris version and almost
all of the options are supported. Unfortunately, it appears to have
made absolutely no difference to our performance numbers. I need
to keep looking for where we are bottle necking.
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do not have __GFP_ZERO set. Once the memory is allocated
then zero out the memory if __GFP_ZERO is passed to
__vmem_alloc.
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ensure I never add anything to the stack I don't absolutely need.
All this debug code could be removed from a production build
anyway so I'm not so worried about the performance impact. We
may also consider revisting the mutex and condvar implementation
to ensure no additional stack is used there.
Initial indications are I have reduced the worst case stack
usage to 9080 bytes. Still to large for the default 8k stacks
so I have been forced to run with 16k stacks until I can
reduce the worst offenders.
git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@83 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c
process of destroying the stacks. Threshhold set fairly aggressively
top 80% of stack usage.
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- Replacing all BUG_ON()'s with proper ASSERT()'s
- Using ENTRY,EXIT,GOTO, and RETURN macro to instument call paths
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changes bring over everything lustre had for debugging with
two exceptions. I dropped by the debug daemon and upcalls
just because it made things a little easier. They can be
readded easily enough if we feel they are needed.
Everything compiles and seems to work on first inspection
but I suspect there are a handful of issues still lingering
which I'll be sorting out right away. I just wanted to get
all these changes commited and safe. I'm getting a little
paranoid about losing them.
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think this should fix anything but it's a good idea regardless.
- Drop the lock before calling the construct/destructor for the slab
otherwise we can't sleep in a constructor/destructor and for long running
functions we may NMI.
- Do something braindead, but safe for the console debug logs for now.
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This way we don't have to contend with superious wakeups which
it appears ZFS is not so careful to handle anyway. So this is
probably for the best.
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function just to be extra safety and paranoid.
- Rewrite the thread shim to take full advantage of the
new kernel kthread API. This greatly simplifies things.
- Add a new regression test for thread_exit() to ensure
it properly terminates a thread immediately without
allowing futher execution of the thread.
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your task is rescheduled to a different cpu after you've
taken the lock but before calling RW_LOCK_HELD is called.
We need the spinlock to ensure there is a wmb() there.
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We need to use kthread_create() here for a few reasons. First
off to old kernel_thread() API functioin will be going away.
Secondly, and more importantly if I use kthread_create() we can
then properly implement a thread_exit() function which terminates
the kernel thread at any point with do_exit(). This fixes our
cleanup bug which was caused by dropping a mutex twice after
thread_exit() didn't really exit.
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atomic operations will be rewritten anyway with the correct arch
specific assembly. But not today.
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- Added liunx block device headers to sunldi.h
- Made __taskq_dispatch safe for interrupt context where it turns out we
need to be useing it.
- Fixed NULL const/dest bug for kmem slab caches
- Places debug __dprintf debugging messages under a spin_lock_irqsave
so it's safe to use then in interrupt handlers. For debugging only!
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Solaris man page. Anyway, since apparently this usage is accectable
I've updated the function to handle it.
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it should be dropped to one page but in the short term we should be able
to easily live with 4 page allocations.
Fix the nvlist bug, it turns out the user space side of things were
packing the nvlists correctly as little endian, and the kernel space
side of things due to a missing #define were unpacking them as big endian.
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what I would call effecient but it does have the advantage
of being correct which is all I need right now. I added
a regression test as well.
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- Enhanse the VERIFY() support to output the values which
failed to compare as expected before crashing. This make
debugging much much much easier.
git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@55 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c
This should handle the absolute minimum I need for ZFS. It will
register the chdev with the right callbacks. Then the generic
registered linux callback will find the right registered solaris
callback for the function and munge the args just right before
passing it on. Should work, but untested (just compiled), so I
expect bugs.
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stuff which only inclused the getf()/releasef() in to the vnode area
where it will only really be used. These calls allow a user to
grab an open file struct given only the known open fd for a particular
user context. ZFS makes use of these, but they're a bit tricky to
test from within the kernel since you already need the file open
and know the fd. So we basically spook the system calls to setup
the environment we need for the splat test case and verify given
just the know fd we can get the file, create the needed vnode, and
then use the vnode interface as usual to read and write from it.
While I was hacking away I also noticed a NULL termination issue
in the second kobj test case so I fixed that too. In fact, I fixed
a few other things as well but all for the best!
git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@51 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c
Adjust kmem slab interface to make a copy of the slab name before
passing it on to the linux slab (we free it latter too)
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- Map the LE/BE_* byteorder macros to the linux versions
- More minor vnodes fixes
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- Re-implmented kobj support based on the vnode support.
- Add TESTS option to check.sh, and removed delay after module load.
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Update check.sh script to take V=1 env var so you can run it verbosely as
follows if your chasing something: sudo make check V=1
Add new kobj api and needed regression tests to allow reading of files from
within the kernel. Normally thats not something I support but the spa layer
needs the support for its config file.
Add some more missing stub headers
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Add sloopy atomic declaration which will need to be fixed (eventually)
Fill out more of the Solaris VM hooks
Adjust the create_thread function
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added a few more stub headers,
fleshed out a few stub headers,
added a FIXME file,
added various compatibility macros
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in what the contents need to be as I encounter the warnings
about missing prototypes, symbols, and such.
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muck with #includes in existing Solaris style source to get it
to find the right stuff.
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