If we're about to return to userspace after performing some swap
readahead, the pages in the deferred-addition LRU queues could stay
there for some time.  So drain them after performing readahead.

Use lru_cache_add_active() so ensure that pages which are, or will be
mapped into pagetables are started out on the active list.

This is the first in a series of patches which tune up the 2.5
performance under heavy swap loads.

Throughput on stupid swapstormy tests is increased by 1.5x to 3x.
Still about 20% behind 2.4 with multithreaded tests.  That is not
easily fixable - the virtual scan tends to apply a form of load
control: particular processes are heavily swapped out so the others can
get ahead.  With 2.5 all processes make very even progress and much
more swapping is needed.  It's on par with 2.4 for single-process
swapstorms.


In this patch:

The code which tries to start mapped pages out on the active list
doesn't work very well.  It uses an "is it mapped into pagetables"
test.  Which doesn't work for, say, swap readahead pages.  They are not
mapped into pagetables when they are spilled onto the LRU.

So create a new `lru_cache_add_active()' function for deferred addition
of pages to their active list.

Also move mark_page_accessed() from filemap.c to swap.c where all
similar functions live.  And teach it to not try to move pages which
are in the deferred-addition list onto the active list.  That won't
work, and it's bogusly clearing PageReferenced in that case.

The deferred-addition lists are a pest.  But lru_cache_add used to be
really expensive in sime workloads on some machines.  Must persist.

Davem said:

"Ho hum, it is tricky :-)))

 At bio_map_user() you need to see the user's most recent write to the
 page if you are going "user --> device".  So if "user --> device"
 bio_map_user() must flush_dcache_page().

 I find the write_to_vm condition confusion which is probably why I am
 sitting here spelling this out :-)

 At bio_unmap_user(), if we are going "device --> user" you have to
 flush_dcache_page().  And actually, this flush could just as
 legitimately occur at bio_map_user() time.

 Therefore, the easiest thing to do is always flush_dcache_page() at
 bio_map_user().

 All the other cases are going to be like this, so we might as well
 cut to the chase and flush_dcache_page() for all the pages inside of
 get_user_pages()."

Tuned for gcc-2.95.3:

	filemap.c:	10815 -> 10046
	highmem.c:	3392 -> 3104
	mmap.c:		5998 -> 5854
	mremap.c:	3058 -> 2802
	msync.c:	1521 -> 1489
	page_alloc.c:	8487 -> 8167

[I was going to send shared pagetables today, but it failed in
 my testing under X :( ]

the first one is an mmap inefficiency that was reported by Saurabh Desai.
The test_str02 NPTL test-utility does the following: it tests the maximum
number of threads by creating a new thread, which thread creates a new
thread itself, etc. It basically creates thousands of parallel threads,
which means thousands of thread stacks.

NPTL uses mmap() to allocate new default thread stacks - and POSIX
requires us to install a 'guard page' as well, which is done via
mprotect(PROT_NONE) on the first page of the stack. This means that tons
of NPTL threads means 2* tons of vmas per MM, all allocated in a forward
fashion starting at the virtual address of 1 GB (TASK_UNMAPPED_BASE).

Saurabh reported a slowdown after the first couple of thousands of
threads, which i can reproduce as well. The reason for this slowdown is
the get_unmapped_area() implementation, which tries to achieve the most
compact virtual memory allocation, by searching for the vma at
TASK_UNMAPPED_BASE, and then linearly searching for a hole. With thousands
of linearly allocated vmas this is an increasingly painful thing to do ...

obviously, high-performance threaded applications will create stacks
without the guard page, which triggers the anon-vma merging code so we end
up with one large vma, not tons of small vmas.

it's also possible for userspace to be smarter by setting aside a stack
space and keeping a bitmap of allocated stacks and using MAP_FIXED (this
also enables it to do the guard page not via mprotect() but by keeping the
stacks apart by 1 page - ie. half the number of vmas) - but this also
decreases flexibility.

So i think that the default behavior nevertheless makes sense as well, so
IMO we should optimize it in the kernel.

there are various solutions to this problem, none of which solve the
problem in a 100% sufficient way, so i went for the simplest approach: i
added code to cache the 'last known hole' address in mm->free_area_cache,
which is used as a hint to get_unmapped_area().

this fixed the test_str02 testcase wonderfully, thread creation
performance for this testcase is O(1) again, but this simpler solution
obviously has a number of weak spots, and the (unlikely but possible)
worst-case is quite close to the current situation. In any case, this
approach does not sacrifice the perfect VM compactness out mmap()
implementation achieves, so it's a performance optimization with no
externally visible consequences.

The most generic and still perfectly-compact VM allocation solution would
be to have a vma tree for the 'inverse virtual memory space', ie. a tree
of free virtual memory ranges, which could be searched and iterated like
the space of allocated vmas. I think we could do this by extending vmas,
but the drawback is larger vmas. This does not save us from having to scan
vmas linearly still, because the size constraint is still present, but at
least most of the anon-mmap activities are constant sized. (both malloc()
and the thread-stack allocator uses mostly fixed sizes.)

This patch contains some fixes from Dave Miller - on some architectures
it is not posible to evaluate TASK_UNMAPPED_BASE at compile-time.

This is Al's implementation of the Orlov block allocator for ext2.

At least doubles the throughput for the traverse-a-kernel-tree
test and is well tested.

I still need to do the ext3 version.

No effort has been put into tuning it at this time, so more gains
are probably possible.

into home.transmeta.com:/home/torvalds/v2.5/linux

This allows subsystems to exist the hierarchy, but not be exported via
the filesystem. This fixes a minor flaw with partitions, as partition
objects are children of block devices, though they register with the 
partition subsystem. Really, the partition subsystem shouldn't have 
presence in the tree at all, yet still exist.

into home.transmeta.com:/home/torvalds/v2.5/linux

into home.transmeta.com:/home/torvalds/v2.5/linux

- replace driver_dir_entry in acpi_device with struct kobject.
- register acpi with firmware subsystem on startup.
- register sub-subsystem.
- put namespace hierarchy under that.

into penguin.transmeta.com:/home/penguin/torvalds/repositories/kernel/linux

This patch adds a new device driver to the linux kernel.  It is for TV
cards based on the Philips SAA7134 chip.  It supports the v4l2 API and
thus depends on the v4l2 patches of the previous mails.

This updates the bttv driver.  Major changes are (a) adaptions to the
final v4l2 API and (b) lots of updates in the card-specific code.  There
are also various other small changes.

This is a update for the tv tuner module.  It makes the descriptions
more verbose and also has some minor bugfixes + cleanups.

This adds the v4l2 API to the linux kernel.

The first, original video4linux API has a number of design bugs.  They
are fixed in this new API revision.  It already exists for quite some
time.  Last weeks it got a number of cleanups based on the experiences
of the last years (drop stuff nobody uses, fix some inconsistencies).
We consider it being in a pretty good shape now and like to see it in
2.6.

This patch is basically the header file with all the structs and ioctls
in there.  A small module with some helper functions for v4l2 drivers is
included too.  Related updates (bttv, ...) will follow as separate
patches.

This updates the video-buf.c module (helper module for video buffer
management).  Some memory management fixes, also some adaptions to the
final v4l2 api.

This implements a pre-decoded wchan in /proc using kallsyms.  I.e.:

        [21:23:17]rml@phantasy:~$ cat /proc/1228/wchan
        wait4

Which, aside from being cool, means procps will not have to parse
Sysyem.map for each process.  In fact, procps will no longer require
System.map.

If CONFIG_KALLSYMS is not enabled, /proc/#/wchan does not exist to
conserve memory.  Regardless of CONFIG_KALLSYMS's value, the old wchan
field in /proc/#/stat still exists.

I have a procps patch I will merge once this is in your tree.

This adds hyper-threading information to /proc/cpuinfo, if relevant: the
physical processor id and the number of sibling units in this core.

The naming of the fields were debated a bit on lkml and the names below
offend the least number of people, do not break glibc, and are the same
as those in 2.4-ac.

This is in 2.4-ac, 2.5-mm, and vendor kernels from RedHat, SuSE, etc.

make x86_do_profile available when UP=y,LOCAL_APIC=n

From Bill Irwin

Optionally back priviled processes' shm with hugetlbfs.

One of the more common requests for and/or users of hugetlb interfaces
in general are databases using shm.  This patch exports functionality
mostly equivalent to tmpfs, adds the calling sequence to ipc/shm.c, and
hashes out a small support function in fs/hugetlbfs/inode.c so that shm
segments may be hugetlbpage-backed if userspace passes a flag to
shmget().

Access to this resource requires CAP_IPC_LOCK.

From Bill Irwin

Tiny hugetlbpage ram-backed filesystem.

Some way to export hugetlbfs through more standard system call
interfaces was needed, and hugetlbfs already had inodes with ratnodes
etc.  used to track offset -> page translations, so adding the rest of
a filesystem around it was easy and natural.  Most of it is identical
to ramfs, except ->f_op->mmap() is now just a wrapper around the
hugetlb_prefault() to fill in the VMA, and to simplify it,
->readpage(), ->prepare_write(), and ->commit_write() are omitted.

Permissions:

(1) check capable(CAP_IPC_LOCK) in ->f_ops->mmap
        This may be redundant but it errors out with less state to
        clean up and at least clarifies the fact that checks are
        being performed at the relevant entry points.

(2) check capable(CAP_IPC_LOCK) in hugetlbfs_zero_setup()
        This is called at shmget() time and is an actual potential
        security hole. hugetlb_prefault() does not perform this
        check itself, so it must be done here.

It's setting the page count on the wrong page.

huge_page_release()             -- hugepage refcounting
free_huge_page()                -- separates freeing from inode refcounting
unmap_hugepage_range()          -- unmapping refcounting hook when locked
zap_hugepage_range()            -- unmappping refcounting hook when unlocked
export setattr_mask()           -- hugetlbfs wants to call it
export destroy_inode()          -- hugetlbfs wants to use it
export unmap_vma()              -- hugetlbpage.c wants to use it
unlock_page() in hugetlbpage.c  -- fixes deadlock in hugetlbfs_truncate()

From Bill Irwin

Move hugetlb and hugetlbfs declarations into a dedicated header file.

Hugetlb's big #ifdeffed block in mm.h got a lot bigger with hugetlbfs.
This patch basically attempts to remove the noise from mm.h by simply
rearranging it into a new header, and fixing all users of hugetlb.

In order for hugetlbfs to operate, prefaulting the vma at mmap()-time
while simultaneously instantiating and performing lookups on its
ratcache entries is needed as an isolated operation.  This is
implemented as part of a different function within hugetlbpage.c that
ties it to inode and key lookup and allocation.

The following patch simply moves the code already present into its own
function, calls it, and makes it available for hugetlbfs to use.

On Wed, 30 Oct 2002, Aaron Lehmann wrote:
>
> Now running 'make oldconfig' or 'make menuconfig' requires a Qt
> installation. I believe that this is a bug because these still work
> fine without Qt when the -k flag is passed to make.

Yes, it's a bug. This fixes it without breaking xconfig.

Also, update path to look for devices in to reflect placement of block
subsystem at top level.