Everywhere except in the pid array we distinguish between a tasks pid and
a tasks tgid (thread group id). Even in the enumeration we want that
distinction sometimes so we have added __PIDTYPE_TGID. With leader_pid
we almost have an implementation of PIDTYPE_TGID in struct signal_struct.
Add PIDTYPE_TGID as a first class member of the pid_type enumeration and
into the pids array. Then remove the __PIDTYPE_TGID special case and the
leader_pid in signal_struct.
The net size increase is just an extra pointer added to struct pid and
an extra pair of pointers of an hlist_node added to task_struct.
The effect on code maintenance is the removal of a number of special
cases today and the potential to remove many more special cases as
PIDTYPE_TGID gets used to it's fullest. The long term potential
is allowing zombie thread group leaders to exit, which will remove
a lot more special cases in the code.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
To access these fields the code always has to go to group leader so
going to signal struct is no loss and is actually a fundamental simplification.
This saves a little bit of memory by only allocating the pid pointer array
once instead of once for every thread, and even better this removes a
few potential races caused by the fact that group_leader can be changed
by de_thread, while signal_struct can not.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
The cost is the the same and this removes the need
to worry about complications that come from de_thread
and group_leader changing.
__task_pid_nr_ns has been updated to take advantage of this change.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
so John Stultz can drop that code.
-----BEGIN PGP SIGNATURE-----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=PDUR
-----END PGP SIGNATURE-----
Merge tag 'please-pull-gettime_vsyscall_update' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux
Pull ia64 update from Tony Luck:
"Stop ia64 being the last holdout using GENERIC_TIME_VSYSCALL_OLD so
that John Stultz can drop that code"
* tag 'please-pull-gettime_vsyscall_update' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux:
ia64: Update fsyscall gettime to use modern vsyscall_update
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
John Stultz provided the outline for this patch back in May 2014 here:
http://patches.linaro.org/patch/30501/
but I let this sit on the shelf for too long and in the intervening
years almost every field in "struct timekeeper" was changed. So this
is almost completely different from his original. Though the key change
in arch/ia64/kernel/fsys.S remains the same.
The core logic change with the updated vsyscall method is that we
preserve the base nanosecond value in shifted nanoseconds, which
allows us to avoid truncating and rounding up to the next nanosecond
every tick to avoid inconsistencies.
Thus the logic moved from
nsec = ((cycle_delta * mult)>>shift) + base_nsec;
to
nsec = ((cycle_delta * mult) + base_snsec) >> shift;
Cc: John Stultz <john.stultz@linaro.org>
Cc: linux-ia64@vger.kernel.org
Signed-off-by: Tony Luck <tony.luck@intel.com>
All the ia64 pvops code is now dead code since both
xen and kvm support have been ripped out [0] [1]. Just
that no one had troubled to rip this stuff out. The only
useful remaining pieces were the old pvops docs but that
was recently also generalized and moved out from ia64 [2].
This has been run time tested on an ia64 Madison system.
[0] 003f7de625 "KVM: ia64: remove" since v3.19-rc1
[1] d52eefb47d "ia64/xen: Remove Xen support for ia64" since v3.14-rc1
[2] "virtual: Documentation: simplify and generalize paravirt_ops.txt"
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
In particular fsys_getppid always returns the ppid in the initial pid
namespace so it does not work for a process in a pid namespace.
Fix from Eric Biederman just removes the fast system call path.
While it is a little bit sad to see another one of these bite
the dust ... I can't imagine that getppid() is really on any
real applications critical path.
Signed-off-by: Tony Luck <tony.luck@intel.com>
If we want to stop the tick further idle, we need to be
able to account the cputime without using the tick.
Virtual based cputime accounting solves that problem by
hooking into kernel/user boundaries.
However implementing CONFIG_VIRT_CPU_ACCOUNTING require
low level hooks and involves more overhead. But we already
have a generic context tracking subsystem that is required
for RCU needs by archs which plan to shut down the tick
outside idle.
This patch implements a generic virtual based cputime
accounting that relies on these generic kernel/user hooks.
There are some upsides of doing this:
- This requires no arch code to implement CONFIG_VIRT_CPU_ACCOUNTING
if context tracking is already built (already necessary for RCU in full
tickless mode).
- We can rely on the generic context tracking subsystem to dynamically
(de)activate the hooks, so that we can switch anytime between virtual
and tick based accounting. This way we don't have the overhead
of the virtual accounting when the tick is running periodically.
And one downside:
- There is probably more overhead than a native virtual based cputime
accounting. But this relies on hooks that are already set anyway.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Currently IA64 has a assembler implementation of sigrtprocmask.
Having a single architecture implement this in assembler language
is a serious maintenance problem that inhibits further evolution of the
signal subsystem. Everyone who wants to do deep changes to signals
would need to learn that assembler language.
Whatever performance improvements IA64 gets from this it cannot be worth
the price in maintainability.
We have some locking problems in signal that need to be fixed,
but this roadblock needs to be removed first.
So just disable the special assembler IA64 implementation and fall back to a
normal syscall there.
Acked-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
GETCPU(2) says:
int getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache);
...
When either cpu or node is NULL nothing is written to the respective pointer.
But the fast system call path had no checks for NULL, and would
thus return -EFAULT if either (or both) of these were NULL.
Reported-by: Mike Frysinger <vapier@gentoo.org>
Tested-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Pull timer core updates from Thomas Gleixner.
* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
ia64: vsyscall: Add missing paranthesis
alarmtimer: Don't call rtc_timer_init() when CONFIG_RTC_CLASS=n
x86: vdso: Put declaration before code
x86-64: Inline vdso clock_gettime helpers
x86-64: Simplify and optimize vdso clock_gettime monotonic variants
kernel-time: fix s/then/than/ spelling errors
time: remove no_sync_cmos_clock
time: Avoid scary backtraces when warning of > 11% adj
alarmtimer: Make sure we initialize the rtctimer
ntp: Fix leap-second hrtimer livelock
x86, tsc: Skip refined tsc calibration on systems with reliable TSC
rtc: Provide flag for rtc devices that don't support UIE
ia64: vsyscall: Use seqcount instead of seqlock
x86: vdso: Use seqcount instead of seqlock
x86: vdso: Remove bogus locking in update_vsyscall_tz()
time: Remove bogus comments
time: Fix change_clocksource locking
time: x86: Fix race switching from vsyscall to non-vsyscall clock
Disintegrate asm/system.h for IA64.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Tony Luck <tony.luck@intel.com>
cc: linux-ia64@vger.kernel.org
The update of the vdso data happens under xtime_lock, so adding a
nested lock is pointless. Just use a seqcount to sync the readers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Tony's fix (f574c84319) has a small bug,
it incorrectly uses "r3" as a scratch register in the first of the two
unlock paths ... it is also inefficient. Optimize the fast path again.
Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Signed-off-by: Tony Luck <tony.luck@intel.com>
When ia64 converted to using ticket locks, an inline implementation
of trylock/unlock in fsys.S was missed. This was not noticed because
in most circumstances it simply resulted in using the slow path because
the siglock was apparently not available (under old spinlock rules).
Problems occur when the ticket spinlock has value 0x0 (when first
initialised, or when it wraps around). At this point the fsys.S
code acquires the lock (changing the 0x0 to 0x1. If another process
attempts to get the lock at this point, it will change the value from
0x1 to 0x2 (using new ticket lock rules). Then the fsys.S code will
free the lock using old spinlock rules by writing 0x0 to it. From
here a variety of bad things can happen.
Signed-off-by: Tony Luck <tony.luck@intel.com>
Add two hooks, paravirt_get_fsyscall_table() and
paravirt_get_fsys_bubble_doen() to paravirtualize fsyscall implementation.
This patch just add the hooks fsyscall and don't paravirtualize it.
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Tony Luck <tony.luck@intel.com>
The sys_getpid() and sys_set_tid_address() behavior changed from
return current->tgid
to
struct pid *pid;
pid = current->pids[PIDTYPE_PID].pid;
return pid->numbers[pid->level].nr;
But the fast system calls on ia64 still operate the old way. Patch them
appropriately to let ia64 work with pid namespaces. Besides, this is one more
step in deprecating of pid and tgid on task_struct.
The fsys_getppid() is to be patched as well, but its logic is much
more complex now, so I will make it later.
One thing I'm not 100% sure is the trick with the IA64_UPID_SHIFT. On order
to access the pid->level's element of an array I have to perform the following
calculations
pid + sizeof(struct upid) * pid->level
The problem is that ia64 can only multiply float point registers, while all
the offsets I have in code are in rXX ones. Fortunately, the sizeof(struct
upid) is 32 bytes on ia64 (and is very unlikely to ever change), so the
calculations get simpler:
pid + pid->level << 5
So, I introduce the IA64_UPID_SHIFT and use the shl instruction. I also
looked at how gcc compiles the similar place and found that it makes it with
shift as well. Is this OK to do so?
Tested with ski emulator with 2.6.24 kernel, but fits 2.6.25-rc4 and
2.6.25-rc4-mm1 as well.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: David Mosberger-Tang <davidm@hpl.hp.com>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Amy Griffis <amy.griffis@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This patch does:
- Remove outdated comments (which someday I marked with "?").
- Reassemble instructions to fit them in fewer bundles.
- If McKinley Errata 9 workaround is not needed, the workaround
bundles will be patched out with NOPs. However it also not
needed to have a totally NOP bundle (nop * 3) before branch.
As a result, this makes the code path 3 (or 2) bundles shorter
(and remove 1 unnecessary stop bit). It seems to be 1% faster.
(10sec loop test, with nojitter @ Madison 1.5GHz x 4)
Before:
CPU 0: 0.14 (usecs) (0 errors / 69598875 iterations)
CPU 1: 0.14 (usecs) (0 errors / 69630721 iterations)
CPU 2: 0.14 (usecs) (0 errors / 69607850 iterations)
CPU 3: 0.14 (usecs) (0 errors / 69619832 iterations)
After:
CPU 0: 0.14 (usecs) (0 errors / 70257728 iterations)
CPU 1: 0.14 (usecs) (0 errors / 70309498 iterations)
CPU 2: 0.14 (usecs) (0 errors / 70280639 iterations)
CPU 3: 0.14 (usecs) (0 errors / 70260682 iterations)
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This patch implements VIRT_CPU_ACCOUNTING for ia64,
which enable us to use more accurate cpu time accounting.
The VIRT_CPU_ACCOUNTING is an item of kernel config, which s390
and powerpc arch have. By turning this config on, these archs
change the mechanism of cpu time accounting from tick-sampling
based one to state-transition based one.
The state-transition based accounting is done by checking time
(cycle counter in processor) at every state-transition point,
such as entrance/exit of kernel, interrupt, softirq etc.
The difference between point to point is the actual time consumed
during in the state. There is no doubt about that this value is
more accurate than that of tick-sampling based accounting.
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This is a merge of Peter Keilty's initial patch (which was
revived by Bob Picco) for this with Hidetoshi Seto's fixes
and scaling improvements.
Acked-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
The ".acq" semantics of the load only apply w.r.t. other data access.
Reading the clock (ar.itc) isn't a data access so strange things can
happen here. Specifically the read of ar.itc can be launched as soon
as the read of xtime_lock.sequence is ISSUED. Since this may cache
miss, and that might cause a thread switch, and there may be cache
contention for the line containing xtime_lock, it may be a long time
before the actual value is returned, so the ar.itc value may be very
stale.
Move the consumption of r28 up before the read of ar.itc to make sure
that we really have got the current value of xtime_lock.sequence
before look at ar.itc.
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
On 1.6GHz Montectio Tiger4, the following performance data is measured with
kernel built with defconfig which has NUMA configured:
Fastest sys_getcpu: 502 itc counts.
Fastest fsys_getcpu: 28 itc counts.
fsys_getcpu performance is largly impacted by whether data (node_to_cpu_map
etc) is in cache. It can take fsys_getcpu up to ~150 itc counts in cold
cache case.
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
beautify coding style for zeroing end of fsyscall_table entries.
Remove misleading __NR_syscall_last and add more comments.
Drop (now unneeded) "guard against failure to increase NR_syscalls"
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
When this new syscall was added to ia64 in commit
39743889aa
fsys.S was forgotten. Add a ".data8 0" there to keep
it in step. [Reported by Stephane Eranian]
Signed-off-by: Tony Luck <tony.luck@intel.com>
Delete obsolete stuff from arch Makefile
Rename file to asm-offsets.h
The trick used in the arch Makefile to circumvent the circular
dependency is kept.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
current->blocked will be set to the value of current->thread_info->flags if the
cmpxchg to update thread_info->flags fails. For performance reasons the store into
current->blocked was placed in the cmpxchg loop. However, the cmpxchg overwrites the
register holding the value to be stored. In the rare case of a retry the value of
thread_info->flags will be written into current->blocked.
The fix is to use another register so that the register containing the current->blocked
value is not overwritten.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Attached is a patch against David's audit.17 kernel that adds checks
for the TIF_SYSCALL_AUDIT thread flag to the ia64 system call and
signal handling code paths.The patch enables auditing of system
calls set up via fsys_bubble_down, as well as ensuring that
audit_syscall_exit() is called on return from sigreturn.
Neglecting to check for TIF_SYSCALL_AUDIT at these points results in
incorrect information in audit_context, causing frequent system panics
when system call auditing is enabled on an ia64 system.
Signed-off-by: Amy Griffis <amy.griffis@hp.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
This patch changes comments & formatting only. There is no code
change.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Improvements come from eliminating srlz.i, not scheduling AR/CR-reads
too early (while there are others still pending), scheduling the
backing-store switch as well as possible, splitting the BBB bundle
into a MIB/MBB pair.
Why is it safe to eliminate the srlz.i? Observe
that we used to clear bits ~PSR_PRESERVED_BITS in PSR.L. Since
PSR_PRESERVED_BITS==PSR.{UP,MFL,MFH,PK,DT,PP,SP,RT,IC}, we
ended up clearing PSR.{BE,AC,I,DFL,DFH,DI,DB,SI,TB}. However,
PSR.BE : already is turned off in __kernel_syscall_via_epc()
PSR.AC : don't care (kernel normally turns PSR.AC on)
PSR.I : already turned off by the time fsys_bubble_down gets invoked
PSR.DFL: always 0 (kernel never turns it on)
PSR.DFH: don't care --- kernel never touches f32-f127 on its own
initiative
PSR.DI : always 0 (kernel never turns it on)
PSR.SI : always 0 (kernel never turns it on)
PSR.DB : don't care --- kernel never enables kernel-level breakpoints
PSR.TB : must be 0 already; if it wasn't zero on entry to
__kernel_syscall_via_epc, the branch to fsys_bubble_down
will trigger a taken branch; the taken-trap-handler then
converts the syscall into a break-based system-call.
In other words: all the bits we're clearying are either 0 already or
are don't cares! Thus, we don't have to write PSR.L at all and we
don't have to do a srlz.i either.
Good for another ~20 cycle improvement for EPC-based heavy-weight
syscalls.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
