Junio noticed that 'non-trivial' pushes were failing if executed
using the sliding window mmap changes.  This was somewhat difficult
to track down as the failure was appearing randomly.

It turns out this was a failure caused by the delta base reference
(either ref or offset format) spanning over the end of a mmap window.

The error in pack-objects was we were not recalling use_pack
after the object header was unpacked, and therefore we did not
get the promise of at least 20 bytes in the buffer for the delta
base parsing.  This would case later memcmp() calls to walk into
unassigned address space at the end of the window.

The reason Junio and I had hard time tracking this down in current
Git repositories is we were both probably packing with offset deltas,
which minimized the odds of the delta base reference spanning over
the end of the mmap window.  Stepping back and repacking with
version 1.3.3 (which only supported reference deltas) increased
the likelyhood of seeing the bug.

The correct technique (as used in sha1_file.c) is to invoke
use_pack() after unpack_object_header_gently to ensure we have
enough data available for the delta base decoding.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

When I converted the mmap() call to xmmap() I failed to cleanup the
way this routine handles errors and left some crufty code behind.
This is a small cleanup, suggested by Johannes.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

In some cases we did not even bother to check the return value of
mmap() and just assume it worked.  This is bad, because if we are
out of virtual address space the kernel returned MAP_FAILED and we
would attempt to dereference that address, segfaulting without any
real error output to the user.

We are replacing all calls to mmap() with xmmap() and moving all
MAP_FAILED checking into that single location.  If a mmap call
fails we try to release enough least-recently-used pack windows
to possibly succeed, then retry the mmap() attempt.  If we cannot
mmap even after releasing pack memory then we die() as none of our
callers have any reasonable recovery strategy for a failed mmap.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

If we are about to fail because this process has run out of memory we
should first try to automatically control our appetite for address
space by releasing enough least-recently-used pack windows to gain
back enough memory such that we might actually be able to meet the
current allocation request.

This should help users who have fairly large repositories but are
working on systems with relatively small virtual address space.
Many times we see reports on the mailing list of these users running
out of memory during various Git operations.  Dynamically decreasing
the amount of pack memory used when the demand for heap memory is
increasing is an intelligent solution to this problem.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

If the compiler has asked us to disable use of mmap() on their
platform then we are forced to use git_mmap and its emulation via
pread.  In this case large (e.g. 32 MiB) windows for pack access
are simply too big as a command will wind up reading a lot more
data than it will ever need, significantly reducing response time.

To prevent a high latency when NO_MMAP has been selected we now
use a default of 1 MiB for core.packedGitWindowSize.  Credit goes
to Linus and Junio for recommending this more reasonable setting.

[jc: upcased the name of the symbolic constant, and made another
 hardcoded constant into a symbolic constant while at it. ]
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

This is a basic set of tests for the sliding window mmap.  We mostly
focus on the verify-pack and pack-objects implementations (including
delta reuse) as these commands appear to cover the bulk of the
affected portions of sha1_file.c.

The test cases don't verify the virtual memory size used, as
this can differ from system to system.  Instead it just verifies
that we can run with very low values for core.packedGitLimit and
core.packedGitWindowSize.

Adding pack_report() to the end of both builtin-verify-pack.c and
builtin-pack-objects.c and manually inspecting the statistics output
can help to verify that the total virtual memory size attributed
to pack mmap usage is what one might expect on the current system.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Much like the alloc_report() function can be useful to report on
object allocation statistics while debugging the new pack_report()
function can be useful to report on the behavior of the mmap window
code used for packfile access.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

If a command opens a packfile for only temporary access and does not
install the struct packed_git* into the global packed_git list then
we are unable to unmap any inactive windows within that packed_git,
causing the overall process to exceed core.packedGitLimit.

We cannot force the callers to install their temporary packfile
into the packed_git chain as doing so would allow that (possibly
corrupt but currently being verified) temporary packfile to become
part of the local ODB, which may allow it to be considered for
object resolution when it may not actually be a valid packfile.

So to support unmapping the windows of these temporary packfiles we
also scan the windows of the struct packed_git which was supplied
to use_pack().  Since commands only work with one temporary packfile
at a time scanning the one supplied to use_pack() and all packs
installed into packed_git should cover everything available in
memory.

We also have to be careful to not close the file descriptor of
the packed_git which was handed to use_pack() when all of that
packfile's windows have been unmapped, as we are already past the
open call that would open the packfile and need the file descriptor
to be ready for mmap() after unuse_one_window returns.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

If we are unable to mmap the a region of the packfile with the mmap()
system call there may be a good reason why, such as a closed file
descriptor or out of address space.  Reporting the system level
error message can help to debug such problems.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

We cannot allow a window to be smaller than 2 system pages.
This limitation is necessary to support the feature of use_pack()
where we always supply at least 20 bytes after the offset to help
the object header and delta base parsing routines.

If packedGitWindowSize were allowed to be as small as 1 system page
then we would be completely unable to access an object header which
spanned over a page as we would never be able to arrange a mapping
such that the header was contiguous in virtual memory.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Now that our pack access code's behavior may be altered by the
setting of core.packedGitWindowSize or core.packedGitLimit we need
to make sure these values are set as configured in the repository's
configuration file rather than to their defaults.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

This finally turns on the sliding window behavior for packfile data
access by mapping limited size windows and chaining them under the
packed_git->windows list.

We consider a given byte offset to be within the window only if there
would be at least 20 bytes (one hash worth of data) accessible after
the requested offset.  This range selection relates to the contract
that use_pack() makes with its callers, allowing them to access
one hash or one object header without needing to call use_pack()
for every byte of data obtained.

In the worst case scenario we will map the same page of data twice
into memory: once at the end of one window and once again at the
start of the next window.  This duplicate page mapping will happen
only when an object header or a delta base reference is spanned
over the end of a window and is always limited to just one page of
duplication, as no sane operating system will ever have a page size
smaller than a hash.

I am assuming that the possible wasted page of virtual address
space is going to perform faster than the alternatives, which
would be to copy the object header or ref delta into a temporary
buffer prior to parsing, or to check the window range on every byte
during header parsing.  We may decide to revisit this decision in
the future since this is just a gut instinct decision and has not
actually been proven out by experimental testing.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

To support multiple windows per packfile we need to unmap only one
window at a time from that packfile, leaving any other windows in
place and available for reference.

We treat all windows from all packfiles equally; the least recently
used, not-in-use window across all packfiles will always be closed
first.

If we have unmapped all windows in a packfile then we can also close
the packfile's file descriptor as its possible we won't need to map
any window from that file in the near future.  This decision about
when to close the pack file descriptor may need to be revisited in
the future after additional testing on several different platforms
can be performed.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

When we parse the object header or the delta base reference we
don't bother to loop over use_pack() calls.  The reason we don't
need to bother with calling use_pack for each byte accessed is that
use_pack will always promise us at least 20 bytes (really the hash
size) after the offset.  This promise from use_pack simplifies a
lot of code in the header parsing logic, as well as helps out the
zlib library by ensuring there's always some data for it to consume
during an inflate call.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

When multiple mmaps start getting used for all pack file access it
is not possible to get all data associated with a specific object
in one contiguous memory region.  This limitation prevents simply
passing a single address and length to SHA1_Update or to inflate.

Instead we need to loop until we have processed all data of interest.

As we loop over the data we are always interested in reusing the same
window 'cursor', as the prior window will no longer be of any use
to us.  This allows the use_pack() call to automatically decrement
the use count of the prior window before setting up access for us
to the next window.

Within each loop we need to make use of the available length output
parameter of use_pack() to tell us how many bytes are available in
the current memory region, as we cannot tell otherwise.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Part of the implementation concept of the sliding mmap window for
pack access is to permit multiple windows per pack to be mapped
independently.  Since the inuse_cnt is associated with the mmap and
not with the file, this value is in struct pack_window and needs to
be incremented/decremented for each pack_window accessed by any code.

To faciliate that implementation we need to replace all uses of
use_packed_git() and unuse_packed_git() with a different API that
follows struct pack_window objects rather than struct packed_git.

The way this works is when we need to start accessing a pack for
the first time we should setup a new window 'cursor' by declaring
a local and setting it to NULL:

  struct pack_windows *w_curs = NULL;

To obtain the memory region which contains a specific section of
the pack file we invoke use_pack(), supplying the address of our
current window cursor:

  unsigned int len;
  unsigned char *addr = use_pack(p, &w_curs, offset, &len);

the returned address `addr` will be the first byte at `offset`
within the pack file.  The optional variable len will also be
updated with the number of bytes remaining following the address.

Multiple calls to use_pack() with the same window cursor will
update the window cursor, moving it from one window to another
when necessary.  In this way each window cursor variable maintains
only one struct pack_window inuse at a time.

Finally before exiting the scope which originally declared the window
cursor we must invoke unuse_pack() to unuse the current window (which
may be different from the one that was first obtained from use_pack):

  unuse_pack(&w_curs);

This implementation is still not complete with regards to multiple
windows, as only one window per pack file is supported right now.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

To efficiently support mmaping of multiple regions of the same pack
file we want to keep the pack's file descriptor open while we are
actively working with that pack.  So we are now keeping that file
descriptor in packed_git.pack_fd and closing it only after we unmap
the last window.

This is going to increase the number of file descriptors that are
in use at once, however that will be bounded by the total number of
pack files present and therefore should not be very high.  It is
a small tradeoff which we may need to revisit after some testing
can be done on various repositories and systems.

For code clarity we also want to seperate out the implementation
of how we open a pack file from the implementation which locates
a suitable window (or makes a new one) from the given pack file.
Since this is a rather large delta I'm taking advantage of doing
it now, in a fairly isolated change.

When we open a pack file we need to examine the header and trailer
without having a mmap in place, as we may only need to mmap
the middle section of this particular pack.  Consequently the
verification code has been refactored to make use of the new
read_or_die function.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Like write_or_die read_or_die reads the entire length requested
or it kills the current process with a die call.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Since the index_size and pack_size members of struct packed_git
are the lengths of those corresponding files we should use the
off_t size of the operating system to store these file lengths,
rather than an unsigned long.  This would help in the future should
we ever resurrect Junio's 64 bit index implementation.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

The idea behind the sliding mmap window pack reader implementation
is to have multiple mmap regions active against the same pack file,
thereby allowing the process to mmap in only the active/hot sections
of the pack and reduce overall virtual address space usage.

To implement this we need to refactor the mmap related data
(pack_base, pack_use_cnt) out of struct packed_git and move them
into a new struct pack_window.

We are refactoring the code to support a single struct pack_window
per packfile, thereby emulating the prior behavior of mmap'ing the
entire pack file.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Rather than hardcoding the maximum number of bytes which can be
mmapped from pack files we should make this value configurable,
allowing the end user to increase or decrease this limit on a
per-repository basis depending on the size of the repository
and the capabilities of their operating system.

In general users should not need to manually tune such a low-level
setting within the core code, but being able to artifically limit
the number of bytes which we can mmap at once from pack files will
make it easier to craft test cases for the new mmap sliding window
implementation.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

The unpack_entry_gently function currently has only two callers:
the delta base resolution in sha1_file.c and the main loop of
pack-check.c.  Both of these must change to using unpack_entry
directly when we implement sliding window mmap logic, so I'm doing
it earlier to help break down the change set.

This may cause a slight performance decrease for delta base
resolution as well as for pack-check.c's verify_packfile(), as
the pack use counter will be incremented and decremented for every
object that is unpacked.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

* jc/curl:
  Work around http-fetch built with cURL 7.16.0

When '*.ig' is ignored, and you have two files f.ig and d.ig/foo
in the working tree,

	$ git add .

correctly ignored f.ig but failed to ignore d.ig/foo.  This was
caused by a thinko in an earlier commit 4888c534, when we tried
to allow adding otherwise ignored files.

After reverting that commit, this takes a much simpler approach.
When we have an unmatched pathspec that talks about an existing
pathname, we know it is an ignored path the user tried to add,
so we include it in the set of paths directory walker returned.

This does not let you say "git add -f D" on an ignored directory
D and add everything under D.  People can submit a patch to
further allow it if they want to, but I think it is a saner
behaviour to require explicit paths to be spelled out in such a
case.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

This reverts commit 4888c534.

Signed-off-by: NJakub Narebski <jnareb@gmail.com>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Not that this reveals anything new, but I did test_tick shell
function in test-lib and found it rather cute and nice.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

* jc/utf8:
  t3900: test conversion to non UTF-8 as well
  Rename t3900 test vector file
  UTF-8: introduce i18n.logoutputencoding.
  Teach log family --encoding
  i18n.logToUTF8: convert commit log message to UTF-8
  Move encoding conversion routine out of mailinfo to utf8.c

Conflicts:

	commit.c

This changes the default remote.origin.fetch configuration
created by git-clone so that it allows non-fast-forward updates.

When using the separate-remote layout with reflog enabled, it
does not make much sense to refuse to update the remote tracking
branch just because some of them do not fast-forward.  git-fetch
issues warnings on non-fast-forwardness, and the user can peek
at what the previous state was using the reflog.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Not using reflog for tags/ was very sensible; not giving reflog
for the remotes/ was not.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

In some environments, certain tests have no way of succeeding
due to platform limitation, such as lack of 'unzip' program, or
filesystem that do not allow arbitrary sequence of non-NUL bytes
as pathnames.

You should be able to say something like

	$ cd t
	$ GIT_SKIP_TESTS=t9200.8 t9200-git-cvsexport-commit.sh

and even:

	$ GIT_SKIP_TESTS='t[0-4]??? t91?? t9200.8' make test

to omit such tests.  The value of the environment variable is a
SP separated list of patterns that tells which tests to skip,
and either can match the "t[0-9]{4}" part to skip the whole
test, or t[0-9]{4} followed by ".$number" to say which
particular test to skip.

Note that some tests in the existing test suite rely on previous
test item, so you cannot arbitrarily disable one and expect the
remainder of test to check what the test originally was intended
to check.
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Signed-off-by: NJunio C Hamano <junkio@cox.net>

* jc/make:
  gcc does not necessarily pass runtime libpath with -R

Otherwise, sending the diagnostic to stdout would provoke a
protocol failure.
Signed-off-by: NJim Meyering <jim@meyering.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

The function xdl_refine_conflicts() tries to break down huge
conflicts by doing a diff on the conflicting regions. However,
this does not make sense when one side is empty.

Worse, when one side is not only empty, but after EOF, the code
accessed unmapped memory.

Noticed by Luben Tuikov, Shawn Pearce and Alexandre Julliard, the
latter providing a test case.
Signed-off-by: NJohannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

This looks a bit more pleasant for users.
Signed-off-by: NEric Wong <normalperson@yhbt.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Not sure how I missed this the first time around...
Signed-off-by: NEric Wong <normalperson@yhbt.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

This could be useful in finding new problems and helping users
debug.
Signed-off-by: NEric Wong <normalperson@yhbt.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

We have less code to worry about now.  As a bonus, --revision
can be used to reliably skip parts of history whenever fetch is
run, not just the first time.  I'm not sure why anybody would
want to skip history in the middle, however...

For people (nearly everyone at the moment) without the
do_switch() function in their Perl SVN library, the entire tree
must be refetched if --follow-parent is used and a parent is
found.  Future versions of SVN will have a working do_switch()
function accessible via Perl.

Accessing repositories on the local machine (especially file://
ones) is also slightly slower as a result; but I suspect most
git-svn users will be using it to access remote repositories.
Signed-off-by: NEric Wong <normalperson@yhbt.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Also, fixed an unportable use of 'export'.
Signed-off-by: NEric Wong <normalperson@yhbt.net>
Signed-off-by: NJunio C Hamano <junkio@cox.net>