Well I didn't test that very well.  __page_cache_release() is doing a
__free_page() on a zero-ref page, so __free_pages() sends the refcount
negative and doesn't free it.  With patch #8, page_cache_release()
almost never frees pages, but it must have been leaking a little bit.
Lucky it showed up.

This fixes it, and also adds a missing PageReserved test in put_page().
Which makes put_page() identical to page_cache_release(), but there are
header file woes.  I'll fix that up later.

This trivial patch reorders the unlocking in rq_unlock()... I was
tired of getting stack dumps in my messages file.

isn't ready for it (either during early boot, or at shutdown)

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Make sure to properly reset the state after disconnect

(Karsten Keil)

Newer gcc's don't like string concat with __FUNCTION__, so
use %s and __FUNCTION__ as argument.

Thanks to Rusty for posting the script...

drivers/isdn/hysdn/Config.in was referring to
CONFIG_ISDN_CAPI before it was defined.

Noticed by Greg Banks.

you have applied my independent-pointer patch already, but i think your
CLEARTID variant is the most elegant solution: it reuses a clone argument,
thus reduces the number of arguments and it's also a nice conceptual pair
to the existing SETTID call. And the TID field can be used as a 'usage'
field as well, because the TID (PID) can never be 0, reducing the number
of fields in the TCB. And we can change the userspace locking code to use
the TID field no problem.

Include tgid when finding next_safe in get_pid()

Currently, sanitize_e820_map uses 0x738 bytes of stack.  The patch below
moves the arrays into __initdata, reducing stack usage to 0x34 bytes.

generic_file_write_nolock() is initialising the pagevec too late,
so if we take an early `goto out' the kernel oopses.  O_DIRECT writes
take that path.

I've filtered all submissions to the ID database, merged new ID's from
both 2.4.x and 2.5.x kernels and here is the result -- patch to 2.5.31
pci.ids with all the new stuff. Could you please send it to Linus?
(I would do it myself, but it seems I'll have a lot of work with the
floods in Prague very soon.)

   The following is a simple fix for an array overrun problem in
mpparse.c.  I am working on a multiquad box which has a EISA bus in it
for it's service processor.  It's local bus number is 18 which is > 3
(see quad_local_to_mp_bus_id.  When the NR_CPUS is close the the real
number of cpus adding the EISA bus #18 in the array stomps all over
various things in memory.  The EISA bus does not need to be mapped
anywhere in the kernel for anything.  This patch will not affect non
clustered apic (multiquad) kernels.

Patch by Chuck Lever. Remove the timeout logic from call_reserve.
This improves the overall RPC call ordering, and ensures that soft
tasks don't time out and give up before they have attempted to send
their message down the socket.

Another patch by Chuck Lever. Fixes up some nasty logic in
call_reserveresult().

The following patch is by Chuck Lever, and fixes an an accounting
error in the 'rpc' field in /proc/net/rpc/nfs.

The following patch fixes a typo that appears both in kernel 2.4.19
and 2.5.31

Pleaase reverse deadlocking change to i2c-elektor.c

The remaining source of page-at-a-time activity against
pagemap_lru_lock is the anonymous pagefault path, which cannot be
changed to operate against multiple pages at a time.

But what we can do is to batch up just its adding of pages to the LRU,
via buffering and deferral.

This patch is based on work from Bill Irwin.

The patch changes lru_cache_add to put the pages into a per-CPU
pagevec.  They are added to the LRU 16-at-a-time.

And in the page reclaim code, purge the local CPU's buffer before
starting.  This is mainly to decrease the chances of pages staying off
the LRU for very long periods: if the machine is under memory pressure,
CPUs will spill their pages onto the LRU promptly.

A consequence of this change is that we can have up to 15*num_cpus
pages which are not on the LRU.  Which could have a slight effect on VM
accuracy, but I find that doubtful.  If the system is under memory
pressure the pages will be added to the LRU promptly, and these pages
are the most-recently-touched ones - the VM isn't very interested in
them anyway.

This optimisation could be made SMP-specific, but I felt it best to
turn it on for UP as well for consistency and better testing coverage.

Some fallout from the pagemap_lru_lock changes:

- lru_cache_del() is no longer used.  Kill it.

- page_cache_release() almost never actually frees pages.  So inline
  page_cache_release() and move its rarely-called slow path into (the
  misnamed) mm/swap.c

- update the locking comment in filemap.c.  pagemap_lru_lock used to
  be one of the outermost locks in the VM locking hierarchy.  Now, we
  never take any other locks while holding pagemap_lru_lock.  So it
  doesn't have any relationship with anything.

- put_page() now removes pages from the LRU on the final put.  The
  lock is interrupt safe.

It is expensive for a CPU to take an interrupt while holding the page
LRU lock, because other CPUs will pile up on the lock while the
interrupt runs.

Disabling interrupts while holding the lock reduces contention by an
additional 30% on 4-way.  This is when the only source of interrupts is
disk completion.  The improvement will be higher with more CPUs and it
will be higher if there is networking happening.

The maximum hold time of this lock is 17 microseconds on 500 MHx PIII,
which is well inside the kernel's maximum interrupt latency (which was
100 usecs when I last looked, a year ago).

This optimisation is not needed on uniprocessor, but the patch disables
IRQs while holding pagemap_lru_lock anyway, so it becomes an irq-safe
spinlock, and pages can be moved from the LRU in interrupt context.

pagemap_lru_lock has been renamed to _pagemap_lru_lock to pick up any
missed uses, and to reliably break any out-of-tree patches which may be
using the old semantics.

Convert all the bulk callers of lru_cache_del() to use the batched
pagevec_lru_del() function.

Change truncate_complete_page() to not delete the page from the LRU.
Do it in page_cache_release() instead.  (This reintroduces the problem
with final-release-from-interrupt.  THat gets fixed further on).

This patch changes the truncate locking somewhat.  The removal from the
LRU now happens _after_ the page has been removed from the
address_space and has been unlocked.  So there is now a window where
the shrink_cache code can discover the to-be-freed page via the LRU
list.  But that's OK - the page is clean, its buffers (if any) are
clean.  It's not attached to any mapping.

The patch goes through the various places which were calling
lru_cache_add() against bulk pages and batches them up.

Also.  This whole patch series improves the behaviour of the system
under heavy writeback load.  There is a reduction in page allocation
failures, some reduction in loss of interactivity due to page
allocators getting stuck on writeback from the VM.  (This is still bad
though).

I think it's due to the change here in mpage_writepages().  That
function was originally unconditionally refiling written-back pages to
the head of the inactive list.  The theory being that they should be
moved out of the way of page allocators, who would end up waiting on
them.

It appears that this simply had the effect of pushing dirty, unwritten
data closer to the tail of the inactive list, making things worse.

So instead, if the caller is (typically) balance_dirty_pages() then
leave the pages where they are on the LRU.

If the caller is PF_MEMALLOC then the pages *have* to be refiled.  This
is because VM writeback is clustered along mapping->dirty_pages, and
it's almost certain that the pages which are being written are near the
tail of the LRU.  If they were left there, page allocators would block
on them too soon.  It would effectively become a synchronous write.

Makes mpage_writepages() move pages around on the LRU sixteen-at-a-time
rather than one-at-a-time.

This patch multithreads the main page reclaim function, shrink_cache().

This function used to run under pagemap_lru_lock.  Instead, we grab
that lock, put 32 pages from the LRU into a private list, drop the
pagemap_lru_lock and then proceed to attempt to free those pages.

Any pages which were succesfully reclaimed are batch-freed.  Pages
which were not reclaimed are re-added to the LRU.

This patch reduces pagemap_lru_lock contention on the 4-way by a factor
of thirty.

The shrink_cache() code has been simplified somewhat.

refill_inactive() was being called too often - often just to process
two or three pages.  Fiddled with that so it processes pages at the
same rate, but works on 32 pages at a time.

Added a couple of mark_page_accessed() calls into mm/memory.c from 2.4.
They seem appropriate.

Change the shrink_caches() logic so that it will still trickle through
the active list (via refill_inactive) even if the inactive list is much
larger than the active list.

This is the first patch in a series of eight which address
pagemap_lru_lock contention, and which simplify the VM locking
hierarchy.

Most testing has been done with all eight patches applied, so it would
be best not to cherrypick, please.

The workload which was optimised was: 4x500MHz PIII CPUs, mem=512m, six
disks, six filesystems, six processes each flat-out writing a large
file onto one of the disks.  ie: heavy page replacement load.

The frequency with which pagemap_lru_lock is taken is reduced by 90%.

Lockmeter claims that pagemap_lru_lock contention on the 4-way has been
reduced by 98%.  Total amount of system time lost to lock spinning went
from 2.5% to 0.85%.

Anton ran a similar test on 8-way PPC, the reduction in system time was
around 25%, and the reduction in time spent playing with
pagemap_lru_lock was 80%.

	http://samba.org/~anton/linux/2.5.30/standard/
versus
	http://samba.org/~anton/linux/2.5.30/akpm/

Throughput changes on uniprocessor are modest: a 1% speedup with this
workload due to shortened code paths and improved cache locality.

The patches do two main things:

1: In almost all places where the kernel was doing something with
   lots of pages one-at-a-time, convert the code to do the same thing
   sixteen-pages-at-a-time.  Take the lock once rather than sixteen
   times.  Take the lock for the minimum possible time.

2: Multithread the pagecache reclaim function: don't hold
   pagemap_lru_lock while reclaiming pagecache pages.  That function
   was massively expensive.

One fallout from this work is that we never take any other locks while
holding pagemap_lru_lock.  So this lock conceptually disappears from
the VM locking hierarchy.


So.  This is all basically a code tweak to improve kernel scalability.
It does it by optimising the existing design, rather than by redesign.
There is little conceptual change to how the VM works.

This is as far as I can tweak it.  It seems that the results are now
acceptable on SMP.  But things are still bad on NUMA.  It is expected
that the per-zone LRU and per-zone LRU lock patches will fix NUMA as
well, but that has yet to be tested.


This first patch introduces `struct pagevec', which is the basic unit
of batched work.  It is simply:

struct pagevec {
	unsigned nr;
	struct page *pages[16];
};

pagevecs are used in the following patches to get the VM away from
page-at-a-time operations.

This patch includes all the pagevec library functions which are used in
later patches.

nlmsvc_notify_blocked() is only called via the fl_notify() pointer which
is only called immediately after we already did a locks_delete_block(),
so calling posix_unblock_lock() here is always a NOP.

This patch from Pat Mochel cleans up the hell that was mtrr.c
into something a lot more modular and easy to understand, by
doing the implementation-per-file as has been done to various
other things by Pat and myself over the last months.

It's functionally identical from a kernel internal point of view,
and a userspace point of view, and is basically just a very large
code clean up.

one of the debugging tests triggered a false-positive BUG() when a
detached thread was straced.

it is much cleaner to pass in the address of the user-space VM lock -
this will also enable arbitrary implementations of the stack-unlock, as
the fifth clone() parameter.

It's referenced by mips and mips64 (both far out of date), but never
actually defined anywhere.

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