The current refill logic in refill_inactive_zone() takes an arbitrarily large
number of pages and chops it down to SWAP_CLUSTER_MAX*4, regardless of the
size of the zone.

This has the effect of reducing the amount of refilling of large zones
proportionately much more than of small zones.

We made this change in may 2003 and I'm damned if I remember why.  let's put
it back so we don't truncate the refill count and see what happens.

- prevent nr_scan_inactive from going negative

- compare `count' with SWAP_CLUSTER_MAX, not `max_scan'

- Use ">= SWAP_CLUSTER_MAX", not "> SWAP_CLUSTER_MAX".

From: Nick Piggin <piggin@cyberone.com.au>

Use a "refill_counter" for inactive list scanning, similar to the one used
for active list scanning.  This batches up scanning now that we precisely
balance ratios, and don't round up the amount to be done.

No observed benefits, but I imagine it would lower the acquisition
frequency of the lru locks in some cases, and make codepaths more efficient
in general due to cache niceness.

This is just a random unsubstantiated tuning tweak: don't immediately
throttle page allocators and kwapd when the going is getting heavier: scan a
bit more of the LRU before throttling.

This removes a vestige of the old algorithm.  We don't want to skip zones if
all_zones_ok is true: we've already precalculated which zones need scanning
and this just stops us from ever performing kswapd reclaim from the DMA zone.

As kswapd is now scanning zones in the highmem->normal->dma direction it can
get into competition with the page allocator: kswapd keep on trying to free
pages from highmem, then kswapd moves onto lowmem.  By the time kswapd has
done proportional scanning in lowmem, someone has come in and allocated a few
pages from highmem.  So kswapd goes back and frees some highmem, then some
lowmem again.  But nobody has allocated any lowmem yet.  So we keep on and on
scanning lowmem in response to highmem page allocations.

With a simple `dd' on a 1G box we get:

 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy wa id
 0  3      0  59340   4628 922348    0    0     4 28188 1072   808  0 10 46 44
 0  3      0  29932   4660 951760    0    0     0 30752 1078   441  1  6 30 64
 0  3      0  57568   4556 924052    0    0     0 30748 1075   478  0  8 43 49
 0  3      0  29664   4584 952176    0    0     0 30752 1075   472  0  6 34 60
 0  3      0   5304   4620 976280    0    0     4 40484 1073   456  1  7 52 41
 0  3      0 104856   4508 877112    0    0     0 18452 1074    97  0  7 67 26
 0  3      0  70768   4540 911488    0    0     0 35876 1078   746  0  7 34 59
 1  2      0  42544   4568 939680    0    0     0 21524 1073   556  0  5 43 51
 0  3      0   5520   4608 976428    0    0     4 37924 1076   836  0  7 41 51
 0  2      0   4848   4632 976812    0    0    32 12308 1092    94  0  1 33 66

Simple fix: go back to scanning the zones in the dma->normal->highmem
direction so we meet the page allocator in the middle somewhere.

 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy wa id
 1  3      0   5152   3468 976548    0    0     4 37924 1071   650  0  8 64 28
 1  2      0   4888   3496 976588    0    0     0 23576 1075   726  0  6 66 27
 0  3      0   5336   3532 976348    0    0     0 31264 1072   708  0  8 60 32
 0  3      0   6168   3560 975504    0    0     0 40992 1072   683  0  6 63 31
 0  3      0   4560   3580 976844    0    0     0 18448 1073   233  0  4 59 37
 0  3      0   5840   3624 975712    0    0     4 26660 1072   800  1  8 46 45
 0  3      0   4816   3648 976640    0    0     0 40992 1073   526  0  6 47 47
 0  3      0   5456   3672 976072    0    0     0 19984 1070   320  0  5 60 35

Currently kswapd walks across all zones in dma->normal->highmem order,
performing proportional scanning until all zones are OK.  This means that
pressure against ZONE_NORMAL causes unnecessary reclaim of ZONE_HIGHMEM.

To fix that up we change kswapd so that it walks the zones in the
high->normal->dma direction, skipping zones which are OK.  Once it encounters
a zone which needs some reclaim kswapd will perform proportional scanning
against that zone as well as all the succeeding lower zones.

We scan the lower zones even if they have sufficient free pages.  This is
because

a) the lower zone may be above pages_high, but because of the incremental
   min, the lower zone may still not be eligible for allocations.  That's bad
   because cache in that lower zone will then not be scanned at the correct
   rate.

b) pages in this lower zone are usable for allocations against the higher
   zone.  So we do want to san all the relevant zones at an equal rate.

- If max_scan evaluates to zero due to a very small inactive list and high
  `priority' numbers, we don't want to thrlttle yet.

- In balance_pgdat(), we may end up not scanning any pages because all
  zones happened to be above pages_high.  Avoid throttling in this case too.

When page reclaim is working out how many pages to san in a zone (max-scan)
it presently rounds that number up if it looks too small - for work batching.

Problem is, this can result in excessive scanning against small zones which
have few inactive pages.  So remove it.

Not that it is possible for max_scan to be zero.  That's OK - it'll become
non-zero as the priority increases.

Page reclaim is currently a bit schitzo: sometimes we say "go and scan this
many pages and tell me how many pages were freed" and at other times we say
"go and scan this many pages, but stop if you freed this many".

It makes the logic harder to control and to understand.  This patch coverts
everything into the "go and scan this many pages and tell me how many pages
were freed" model.

It doesn't seem to affect performance much either way.

We currently have a problem with the balancing of reclaim between zones: much
more reclaim happens against highmem than against lowmem.

This patch partially fixes this by changing the direct reclaim path so it
does not bale out of the zone walk after having reclaimed sufficient pages
from highmem: go on to reclaim from lowmem regardless of how many pages we
reclaimed from lowmem.

The patch which went in six months or so back which said "only reclaim slab
if we're scanning lowmem pagecache" was wrong.  I must have been asleep at
the time.

We do need to scan slab in response to highmem page reclaim as well.  Because
all the math is based around the total amount of memory in the machine, and
we know that if we're performing highmem page reclaim then the lower zones
have no free memory.

From: Nick Piggin <piggin@cyberone.com.au>

The logic which calculates the numberof pages which were scanned is mucked
up.  Fix.

From: Nick Piggin <piggin@cyberone.com.au>

In try_to_free_pages(), put even pressure on the slab even if we have
reclaimed enough pages from the LRU.

From: Nick Piggin <piggin@cyberone.com.au>

In shrink_slab(), do the multiply before the divide to avoid losing
precision.

From: Nick Piggin <piggin@cyberone.com.au>

If refill_inactive_zone() is running in its dont-reclaim-mapped-memory mode
we are tossing away the referenced infomation on active mapped pages.

So put that info back if we're not going to deactivate the page.

The logic in balance_pgdat() is all bollixed up.

- the incoming arg `nr_pages' should be used to determine if we're being
  asked to free a specific number of pages, not `to_free'.

- local variable `to_free' is not appropriate for the determination of
  whether we failed to bring all zones to appropriate free pages levels.

  Fix this by correctly calculating `all_zones_ok' and then use
  all_zones_ok to determine whether we need to throttle kswapd.

So the logic now is:


	for (increasing priority) {

		all_zones_ok = 1;

		for (all zones) {
			to_reclaim = number of pages to try to reclaim
				     from this zone;
			max_scan = number of pages to scan in this pass
				   (gets larger as `priority' decreases)
			/*
			 * set `reclaimed' to the number of pages which were
			 * actually freed up
			 */
			reclaimed = scan(max_scan pages);
			reclaimed += shrink_slab();

			to_free -= reclaimed;	/* for the `nr_pages>0' case */

			/*
			 * If this scan failed to reclaim `to_reclaim' or more
			 * pages, we're getting into trouble.  Need to scan
			 * some more, and throttle kswapd.   Note that this
			 * zone may now have sufficient free pages due to
			 * freeing activity by some other process.   That's
			 * OK - we'll pick that info up on the next pass
			 * through the loop.
			 */
			if (reclaimed < to_reclaim)
				all_zones_ok = 0;
		}
		if (to_free > 0)
			continue;	/* swsusp: need to do more work */
		if (all_zones_ok)
			break;		/* kswapd is done */
		/*
		 * OK, kswapd is getting into trouble.  Take a nap, then take
		 * another pass across the zones.
		 */
		blk_congestion_wait();
	}

From: Nikita Danilov <Nikita@Namesys.COM>

Now that decision to reclaim mapped memory is taken on the basis of
zone->prev_priority, priority argument is no longer needed.

From: Nick Piggin <piggin@cyberone.com.au>

The addition of the smp_mb and the other change is to try to close the
window for races a bit.  Obviously they can still happen, it's a racy
interface and it doesn't matter much.

Teach blk_congestion_wait() to return the number of jiffies remaining.  This
is for debug, but it is also nicely consistent.

To check on zone balancing, split the /proc/vmstat:pgsteal, pgreclaim pgalloc
and pgscan stats into per-zone counters.

Additionally, split the pgscan stats into pgscan_direct and pgscan_kswapd to
see who's doing how much scanning.

And add a metric for the number of slab objects which were scanned.

From: Paul Fulghum <paulkf@microgate.com>

* track driver API changes
* remove cast (kernel janitor)

From: Paul Fulghum <paulkf@microgate.com>

* Track driver API changes
* Remove cast (kernel janitor)

From: Paul Fulghum <paulkf@microgate.com>

Patch for synclinkmp.c

* Track driver API changes
* Remove cast (kernel janitor)
* Replace page_free call with kfree (to match kmalloc allocation)

From: Chris Mason <mason@suse.com>

mempool_alloc() and mempool_free() check pool->curr_nr without any locks
held.  This can lead to skipping a wakeup when there are people waiting,
and sleeping when there are free elements in the pool.

I can't trigger this reliably, but sooner or later someone on ppc is
probably going to hit it.

From: Geert Uytterhoeven <geert@linux-m68k.org>

M68k interrupt management: rename routines to not confuse them with
syscalls

- sys_{request,free}_irq() -> cpu_{request,free}_irq()

- q40_sys_default_handler[] -> q40_default_handler

- sys_default_handler() -> default_handler()

From: Geert Uytterhoeven <geert@linux-m68k.org>

Mac IDE: Make sure the core IDE driver doesn't try to request the MMIO
ports a second time, since this will fail.

From: Geert Uytterhoeven <geert@linux-m68k.org>

Apollo fb: Add sysfs support (from James Simmons)

From: Geert Uytterhoeven <geert@linux-m68k.org>

Amiga Framemaster II fb: Add sysfs support (from James Simmons)

From: Geert Uytterhoeven <geert@linux-m68k.org>

Add missing implementation for non-atomic __test_and_set_bit()

From: James Simmons <jsimmons@infradead.org>,
      Kronos <kronos@kronoz.cjb.net>

Various fixes and enhancements to the monitor hardware detection code.  The
only driver that uses it is the radeon driver.

Old EDID parsing code was very verbose, half of the patch address this (ie.
print lots of stuff iff DEBUG).  The other big change is the FB_MODE_IS_*
stuff: we really need a way to know the origin of a video mode.  In this way
we can select video mode that comes from EDID instead of VESA or GTF.

Drivers other than radeonfb won't be affected because they cannot (yet) get
EDID from the monitor and don't use EDID related code.

From: Michel Marti <michel.marti@objectxp.com>

The blkmtd driver oopses in add_device().  The following trivial patch
fixes this.

From: Arjan van de Ven <arjanv@redhat.com>

Readahead of raid0 was suboptimal; it read only 1 stride ahead.  The
problem with this is that while it will keep all spindles busy, it will not
actually manage to make larger IO's, eg each disk would just do the chunk
size IO.  Doing at least 2 chunks is more than appropriate so that each
spindle will get a chance to merge IO's.

(Neil fixed raid6 and raid6 too)

From: Rusty Russell <rusty@rustcorp.com.au>

Someone added __attribute_used__ throughout module.h, but didn't remove the
", unused".  Looks like some arch/gcc combos still consider it unused, and
discard the fn.

From: Geert Uytterhoeven <geert@linux-m68k.org>

Make CONFIG_NVRAM depend on the prerequisites that are explicitly checked
for in drivers/char/nvram.c, or on CONFIG_GENERIC_NVRAM (for PPC).

From: Geert Uytterhoeven <geert@linux-m68k.org>

Add missing include (needed for struct inode)

From: Marc-Christian Petersen <m.c.p@wolk-project.de>

The attached patch is needed to stop showing us "Macintosh device drivers"
for all architectures via menuconfig || xconfig || gconfig.  It's only
necessary for PPC and/or MAC.

ACKed by benh.

From: Arjan van de Ven <arjanv@redhat.com>

Several of the pte_chain_alloc() allocators that use GFP_ATOMIC have a
fallback for failure that sleeps; they thus need to not warn on failure..
Seen during a big fork on a busy system.

From: "Randy.Dunlap" <rddunlap@osdl.org>

cciss_scsi_detect() can be called after init (for TAPE support).

From: Matt Domsch <Matt_Domsch@dell.com>

Patch below from Patrick J. LoPresti and myself.  Patrick describes:

Why this patch?  The problem is that the legacy BIOS interface
(INT13/AH=3D08) for querying the disk geometry returns different values
than the extended INT13 interface which the EDD code currently uses.  This
is because the legacy interface only provides a 10-bit cylinder field, so
modern BIOSes "lie" about the head/sector counts in order to make more of
the disk visible within the first 1024 cylinders.

Many non-Linux applications, including the stock Windows boot loader, DOS
fdisk, etc., rely upon the legacy interface and geometry.  So it is useful
to be able to obtain the legacy values from a running Linux kernel.

What this patch does is to add new entries under
/sys/firmware/edd/int13_devXX named "legacy_cylinders", "legacy_heads", and
"legacy_sectors".  These provide the geometry given by the legacy
INT13/AH=3D08 BIOS interface, just like the current "default_cylinders"
etc.  provide the the geometry given by the INT13/AH=3D48 interface.

Without this patch, I cannot use Linux to partition a drive and install
Windows, which happens to be my application.

 - Pat
   http://unattended.sourceforge.net/

In addition, this adds two buggy BIOS workarounds  in the EDD int13
calls as suggested by Ralf Brown's interrupt list.

I'm also interested in moving this code out of arch/i386/kernel/edd.c and
include/asm-i386/edd.h, as I believe it is applicable on x86-64 as well.
However, there's no good place under drivers/ to put edd.c when it's not
tied to a bus, but to several CPU architectures and their firmwares...
Maybe a new directory drivers/firmware?