vm_pageout_page_stats() from Giant.
- Modify vm_pager_put_pages() and vm_pager_page_unswapped() to expect the
vm object to be locked on entry. (All of the pager routines now expect
this.)
Remove the vnode and dev_t fields and replace them with a void *.
Introduce separate strategy functions for devices and regular (NFS)
vnodes.
For devices we don't need the vnode v_numoutput stuff.
Add a generic swaponsomething() function to add a swapdevice and
split the remainder of swaponvp() into swaponvp() and swapondev()
which calls this backend.
Eliminate a lot of checkes to make sure requests are not cross-device
which is unnecessary with the new layout. We know a sequential request
cannot possibly be cross-device because there is a reserved page between
the devices.
Remove a couple of comments which no longer are relevant.
to not get any cross-device I/O requests. (The unallocated first page
protecting BSD labels already gave us this, but that hack may go away
at some point in time).
Remove the check for cross-device I/O requests in swap_pager_strategy.
Move the repeated statistics updating into flushchainbuf().
Use ->bio_children to count child buffers, rather than abuse the
bio_caller1 pointer.
Expand the relevant bits of waitchainbuf() inline, this clarifies
the code a little bit.
striping to a per device round-robin algorithm.
Because of the policy of not attempting to retain previous swap
allocation on page-out, this means that a newly added swap device
almost instantly takes its 1/N share of the I/O load but it takes
somewhat longer for it to assume it's 1/N share of the pages if there
is plenty of space on the other devices.
Change the 8G total swapspace limitation to 8G per device instead
by using a per device blist rather than one global blist. This
reduces the memory footprint by 75% (typically a couple hundred
kilobytes) for the common case with one swapdevice but NSWAPDEV=4.
Remove the compile time constant limit of number of swap devices,
there is no limit now. Instead of a fixed size array, store the
per swapdev structure in a TAILQ.
Total swap space is still addressed by a 32 bit page number and
therefore the upper limit is now 2^42 bytes = 16TB (for i386).
We still do not allocate the first page of each device in order to
give some amount of protection to any bsdlabel at the start of the
device.
A new device is appended after the existing devices in the swap space,
no attempt is made to fill in holes left behind by swapoff (this can
trivially be changed should it ever become a problem).
The sysctl vm.nswapdev now reflects the number of currently configured
swap devices.
Rename vm_swap_size to swap_pager_avail for consistency with other
exported names.
Change argument type for vm_proc_swapin_all() and swap_pager_isswapped()
to be a struct swdevt pointer rather than an index.
Not changed: we are still using blists to manage the free space,
but since the swapspace is no longer fragmented by the striping
different resource managers might fare better.
contain the filedescriptor number on opens from userland.
The index is used rather than a "struct file *" since it conveys a bit
more information, which may be useful to in particular fdescfs and /dev/fd/*
For now pass -1 all over the place.
the "toss the largest process" emergency handling) from vm_map.c to
swap_pager.c.
The quantity calculated depends strongly on the internals of the
swap_pager and by moving it, we no longer need to expose the
internal metrics of the swap_pager to the world.
paging space and how much of it is in use (in pages).
Use this interface from the Linuxolator instead of groping around in the
internals of the swap_pager.
is not natural and needlessly exposes a lot of dirty laundry.
Move private interfaces between the two from swap_pager.h to swap_pager.c
and staticize as much as possible.
No functional change.
files, so that SWAP_META_PAGES does not vary either.
swap_pager.c ended up with a value of 16, everybody else 8. Go with
the 16 for now.
This should only have any effect in the "kill processes because we
are out of swap" scenario, where it will make some sort of estimate
of something more precise.
types are not required, as the overhead is unnecessary:
o In the i386 pmap_protect(), `sindex' and `eindex' represent page
indices within the 32-bit virtual address space.
o In swp_pager_meta_build() and swp_pager_meta_ctl(), use a temporary
variable to store the low few bits of a vm_pindex_t that gets used
as an array index.
o vm_uiomove() uses `osize' and `idx' for page offsets within a
map entry.
o In vm_object_split(), `idx' is a page offset within a map entry.
most cases NULL is passed, but in some cases such as network driver locks
(which use the MTX_NETWORK_LOCK macro) and UMA zone locks, a name is used.
Tested on: i386, alpha, sparc64
style(9)
- Minor space adjustment in cases where we have "( ", " )", if(), return(),
while(), for(), etc.
- Add /* SYMBOL */ after a few #endifs.
Reviewed by: alc
and isn't strictly required. However, it lowers the number of false
positives found when grep'ing the kernel sources for p_ucred to ensure
proper locking.
- crhold() returns a reference to the ucred whose refcount it bumps.
- crcopy() now simply copies the credentials from one credential to
another and has no return value.
- a new crshared() primitive is added which returns true if a ucred's
refcount is > 1 and false (0) otherwise.
information. The default limits only effect machines with > 1GB of ram
and can be overriden with two new kernel conf variables VM_SWZONE_SIZE_MAX
and VM_BCACHE_SIZE_MAX, or with loader variables kern.maxswzone and
kern.maxbcache. This has the effect of leaving more KVM available for
sizing NMBCLUSTERS and 'maxusers' and should avoid tripups where a sysad
adds memory to a machine and then sees the kernel panic on boot due to
running out of KVM.
Also change the default swap-meta auto-sizing calculation to allocate half
of what it was previously allocating. The prior defaults were way too high.
Note that we cannot afford to run out of swap-meta structures so we still
stay somewhat conservative here.
1) allocate fewer buckets
2) when failing to allocate swap zone, keep reducing the zone by
a third rather than a half in order to reduce the chance of
allocating way too little.
I also moved around some code for readability.
Suggested by: dillon
Reviewed by: dillon
(this commit is just the first stage). Also add various GIANT_ macros to
formalize the removal of Giant, making it easy to test in a more piecemeal
fashion. These macros will allow us to test fine-grained locks to a degree
before removing Giant, and also after, and to remove Giant in a piecemeal
fashion via sysctl's on those subsystems which the authors believe can
operate without Giant.
acquired.
- Assert Giant is held in the strategy, getpages, and putpages methods and
the getchainbuf, flushchainbuf, and waitchainbuf functions.
- Always call flushchainbuf() w/o the VM lock.
vm_mtx does not recurse and is required for most low level
vm operations.
faults can not be taken without holding Giant.
Memory subsystems can now call the base page allocators safely.
Almost all atomic ops were removed as they are covered under the
vm mutex.
Alpha and ia64 now need to catch up to i386's trap handlers.
FFS and NFS have been tested, other filesystems will need minor
changes (grabbing the vm lock when twiddling page properties).
Reviewed (partially) by: jake, jhb
Protect pager object list manipulation with a mutex.
It doesn't look possible to combine them under a single sx lock because
creation may block and we can't have the object list manipulation block
on anything other than a mutex because of interrupt requests.
this information via the vm.nswapdev sysctl (number of swap areas)
and vm.swapdevX nodes (where X is the device), which contain the MIBs
dev, blocks, used, and flags. These changes are required to allow
top and other userland swap-monitoring utilities to run without
setgid kmem.
Submitted by: Thomas Moestl <tmoestl@gmx.net>
Reviewed by: freebsd-audit
struct swblock entries by dividing the number of the entries by 2
until the swap metadata fits.
- Reject swapon(2) upon failure of swap_zone allocation.
This is just a temporary fix. Better solutions include:
(suggested by: dillon)
o reserving swap in SWAP_META_PAGES chunks, and
o swapping the swblock structures themselves.
Reviewed by: alfred, dillon
Removed most of the hacks that were trying to deal with low-memory
situations prior to now.
The new code is based on the concept that I/O must be able to function in
a low memory situation. All major modules related to I/O (except
networking) have been adjusted to allow allocation out of the system
reserve memory pool. These modules now detect a low memory situation but
rather then block they instead continue to operate, then return resources
to the memory pool instead of cache them or leave them wired.
Code has been added to stall in a low-memory situation prior to a vnode
being locked.
Thus situations where a process blocks in a low-memory condition while
holding a locked vnode have been reduced to near nothing. Not only will
I/O continue to operate, but many prior deadlock conditions simply no
longer exist.
Implement a number of VFS/BIO fixes
(found by Ian): in biodone(), bogus-page replacement code, the loop
was not properly incrementing loop variables prior to a continue
statement. We do not believe this code can be hit anyway but we
aren't taking any chances. We'll turn the whole section into a
panic (as it already is in brelse()) after the release is rolled.
In biodone(), the foff calculation was incorrectly
clamped to the iosize, causing the wrong foff to be calculated
for pages in the case of an I/O error or biodone() called without
initiating I/O. The problem always caused a panic before. Now it
doesn't. The problem is mainly an issue with NFS.
Fixed casts for ~PAGE_MASK. This code worked properly before only
because the calculations use signed arithmatic. Better to properly
extend PAGE_MASK first before inverting it for the 64 bit masking
op.
In brelse(), the bogus_page fixup code was improperly throwing
away the original contents of 'm' when it did the j-loop to
fix the bogus pages. The result was that it would potentially
invalidate parts of the *WRONG* page(!), leading to corruption.
There may still be cases where a background bitmap write is
being duplicated, causing potential corruption. We have identified
a potentially serious bug related to this but the fix is still TBD.
So instead this patch contains a KASSERT to detect the problem
and panic the machine rather then continue to corrupt the filesystem.
The problem does not occur very often.. it is very hard to
reproduce, and it may or may not be the cause of the corruption
people have reported.
Review by: (VFS/BIO: mckusick, Ian Dowse <iedowse@maths.tcd.ie>)
Testing by: (VM/Deadlock) Paul Saab <ps@yahoo-inc.com>
Pre-rfork code assumed inherent locking of a process's file descriptor
array. However, with the advent of rfork() the file descriptor table
could be shared between processes. This patch closes over a dozen
serious race conditions related to one thread manipulating the table
(e.g. closing or dup()ing a descriptor) while another is blocked in
an open(), close(), fcntl(), read(), write(), etc...
PR: kern/11629
Discussed with: Alexander Viro <viro@math.psu.edu>
in the face of non-stripe-aligned swap areas. The bug could cause a
panic during boot.
Refuse to configure a swap area that is too large (67 GB or so)
Properly document the power-of-2 requirement for SWB_NPAGES.
The patch is slightly different then the one Tor enclosed in the P.R.,
but accomplishes the same thing.
PR: kern/20273
Submitted by: Tor.Egge@fast.no
to various pmap_*() functions instead of looking up the physical address
and passing that. In many cases, the first thing the pmap code was doing
was going to a lot of trouble to get back the original vm_page_t, or
it's shadow pv_table entry.
Inspired by: John Dyson's 1998 patches.
Also:
Eliminate pv_table as a seperate thing and build it into a machine
dependent part of vm_page_t. This eliminates having a seperate set of
structions that shadow each other in a 1:1 fashion that we often went to
a lot of trouble to translate from one to the other. (see above)
This happens to save 4 bytes of physical memory for each page in the
system. (8 bytes on the Alpha).
Eliminate the use of the phys_avail[] array to determine if a page is
managed (ie: it has pv_entries etc). Store this information in a flag.
Things like device_pager set it because they create vm_page_t's on the
fly that do not have pv_entries. This makes it easier to "unmanage" a
page of physical memory (this will be taken advantage of in subsequent
commits).
Add a function to add a new page to the freelist. This could be used
for reclaiming the previously wasted pages left over from preloaded
loader(8) files.
Reviewed by: dillon
<sys/bio.h>.
<sys/bio.h> is now a prerequisite for <sys/buf.h> but it shall
not be made a nested include according to bdes teachings on the
subject of nested includes.
Diskdrivers and similar stuff below specfs::strategy() should no
longer need to include <sys/buf.> unless they need caching of data.
Still a few bogus uses of struct buf to track down.
Repocopy by: peter
a struct buf. Don't try to examine B_ASYNC, it is a layering violation
to do so. The only current user of this interface is vn(4) which, since
it emulates a disk interface, operates on struct bio already.
