15 Oct, 2010
1 commit
-
akiphie points out that a.out core-dumps have that odd task struct
dumping that was never used and was never really a good idea (it goes
back into the mists of history, probably the original core-dumping
code). Just remove it.Also do the access_ok() check on dump_write(). It probably doesn't
matter (since normal filesystems all seem to do it anyway), but he
points out that it's normally done by the VFS layer, so ...[ I suspect that we should possibly do "vfs_write()" instead of
calling ->write directly. That also does the whole fsnotify and write
statistics thing, which may or may not be a good idea. ]And just to be anal, do this all for the x86-64 32-bit a.out emulation
code too, even though it's not enabled (and won't currently even
compile)Reported-by: akiphie
Signed-off-by: Linus Torvalds
30 Mar, 2010
1 commit
-
…it slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
25 Mar, 2010
1 commit
-
fs/binfmt_aout.c: In function `aout_core_dump':
fs/binfmt_aout.c:125: warning: passing argument 2 of `dump_write' makes pointer from integer without a cast
include/linux/coredump.h:12: note: expected `const void *' but argument is of type `long unsigned int'
fs/binfmt_aout.c:132: warning: passing argument 2 of `dump_write' makes pointer from integer without a cast
include/linux/coredump.h:12: note: expected `const void *' but argument is of type `long unsigned int'due to dump_write() expecting a user void *. Fold casts into the
START_DATA/START_STACK macros and shut up the warnings.Signed-off-by: Borislav Petkov
Cc: Daisuke HATAYAMA
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
07 Mar, 2010
3 commits
-
My next patch will replace ELF_CORE_EXTRA_* macros by functions, putting
them into other newly created *.c files. Then, each files will contain
dump_write(), where each pair of binfmt_*.c and elfcore.c should be the
same. So, this patch moves them into a header file with dump_seek().
Also, the patch deletes confusing DUMP_WRITE macros in each files.Signed-off-by: Daisuke HATAYAMA
Cc: "Luck, Tony"
Cc: Jeff Dike
Cc: David Howells
Cc: Greg Ungerer
Cc: Roland McGrath
Cc: Oleg Nesterov
Cc: Ingo Molnar
Cc: Alexander Viro
Cc: Andi Kleen
Cc: Alan Cox
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The current ELF dumper can produce broken corefiles if program headers
exceed 65535. In particular, the program in 64-bit environment often
demands more than 65535 mmaps. If you google max_map_count, then you can
find many users facing this problem.Solaris has already dealt with this issue, and other OSes have also
adopted the same method as in Solaris. Currently, Sun's document and AMD
64 ABI include the description for the extension, where they call the
extension Extended Numbering. See Reference for further information.I believe that linux kernel should adopt the same way as they did, so I've
written this patch.I am also preparing for patches of GDB and binutils.
How to fix
==========In new dumping process, there are two cases according to weather or
not the number of program headers is equal to or more than 65535.- if less than 65535, the produced corefile format is exactly the same
as the ordinary one.- if equal to or more than 65535, then e_phnum field is set to newly
introduced constant PN_XNUM(0xffff) and the actual number of program
headers is set to sh_info field of the section header at index 0.Compatibility Concern
=====================* As already mentioned in Summary, Sun and AMD64 has already adopted
this. See Reference.* There are four combinations according to whether kernel and userland
tools are respectively modified or not. The next table summarizes
shortly for each combination.---------------------------------------------
Original Kernel | Modified Kernel
---------------------------------------------
< 65535 | >= 65535 | < 65535 | >= 65535
-------------------------------------------------------------
Original Tools | OK | broken | OK | broken (#)
-------------------------------------------------------------
Modified Tools | OK | broken | OK | OK
-------------------------------------------------------------Note that there is no case that `OK' changes to `broken'.
(#) Although this case remains broken, O-M behaves better than
O-O. That is, while in O-O case e_phnum field would be extremely
small due to integer overflow, in O-M case it is guaranteed to be at
least 65535 by being set to PN_XNUM(0xFFFF), much closer to the
actual correct value than the O-O case.Test Program
============Here is a test program mkmmaps.c that is useful to produce the
corefile with many mmaps. To use this, please take the following
steps:$ ulimit -c unlimited
$ sysctl vm.max_map_count=70000 # default 65530 is too small
$ sysctl fs.file-max=70000
$ mkmmaps 65535Then, the program will abort and a corefile will be generated.
If failed, there are two cases according to the error message
displayed.* ``out of memory'' means vm.max_map_count is still smaller
* ``too many open files'' means fs.file-max is still smaller
So, please change it to a larger value, and then retry it.
mkmmaps.c
==
#include
#include
#include
#include
#include
int main(int argc, char **argv)
{
int maps_num;
if (argc < 2) {
fprintf(stderr, "mkmmaps [number of maps to be created]\n");
exit(1);
}
if (sscanf(argv[1], "%d", &maps_num) == EOF) {
perror("sscanf");
exit(2);
}
if (maps_num < 0) {
fprintf(stderr, "%d is invalid\n", maps_num);
exit(3);
}
for (; maps_num > 0; --maps_num) {
if (MAP_FAILED == mmap((void *)NULL, (size_t) 1, PROT_READ,
MAP_SHARED | MAP_ANONYMOUS, (int) -1,
(off_t) NULL)) {
perror("mmap");
exit(4);
}
}
abort();
{
char buffer[128];
sprintf(buffer, "wc -l /proc/%u/maps", getpid());
system(buffer);
}
return 0;
}Tested on i386, ia64 and um/sys-i386.
Built on sh4 (which covers fs/binfmt_elf_fdpic.c)References
==========- Sun microsystems: Linker and Libraries.
Part No: 817-1984-17, September 2008.
URL: http://docs.sun.com/app/docs/doc/817-1984- System V ABI AMD64 Architecture Processor Supplement
Draft Version 0.99., May 11, 2009.
URL: http://www.x86-64.org/This patch:
There are three different definitions for dump_seek() functions in
binfmt_aout.c, binfmt_elf.c and binfmt_elf_fdpic.c, respectively. The
only for binfmt_elf.c.My next patch will move dump_seek() into a header file in order to share
the same implementations for dump_write() and dump_seek(). As the first
step, this patch unify these three definitions for dump_seek() by applying
the past commits that have been applied only for binfmt_elf.c.Specifically, the modification made here is part of the following commits:
* d025c9db7f31fc0554ce7fb2dfc78d35a77f3487
* 7f14daa19ea36b200d237ad3ac5826ae25360461This patch does not change a shape of corefiles.
Signed-off-by: Daisuke HATAYAMA
Cc: "Luck, Tony"
Cc: Jeff Dike
Cc: David Howells
Cc: Greg Ungerer
Cc: Roland McGrath
Cc: Oleg Nesterov
Cc: Ingo Molnar
Cc: Alexander Viro
Cc: Andi Kleen
Cc: Alan Cox
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Make sure compiler won't do weird things with limits. E.g. fetching them
twice may return 2 different values after writable limits are implemented.I.e. either use rlimit helpers added in commit 3e10e716abf3 ("resource:
add helpers for fetching rlimits") or ACCESS_ONCE if not applicable.Signed-off-by: Jiri Slaby
Cc: Alexander Viro
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
30 Jan, 2010
1 commit
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'flush_old_exec()' is the point of no return when doing an execve(), and
it is pretty badly misnamed. It doesn't just flush the old executable
environment, it also starts up the new one.Which is very inconvenient for things like setting up the new
personality, because we want the new personality to affect the starting
of the new environment, but at the same time we do _not_ want the new
personality to take effect if flushing the old one fails.As a result, the x86-64 '32-bit' personality is actually done using this
insane "I'm going to change the ABI, but I haven't done it yet" bit
(TIF_ABI_PENDING), with SET_PERSONALITY() not actually setting the
personality, but just the "pending" bit, so that "flush_thread()" can do
the actual personality magic.This patch in no way changes any of that insanity, but it does split the
'flush_old_exec()' function up into a preparatory part that can fail
(still called flush_old_exec()), and a new part that will actually set
up the new exec environment (setup_new_exec()). All callers are changed
to trivially comply with the new world order.Signed-off-by: H. Peter Anvin
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds
18 Dec, 2009
1 commit
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Introduce coredump parameter data structure (struct coredump_params) to
simplify binfmt->core_dump() arguments.Signed-off-by: Masami Hiramatsu
Suggested-by: Ingo Molnar
Cc: Hidehiro Kawai
Cc: Oleg Nesterov
Cc: Roland McGrath
Cc: KOSAKI Motohiro
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
04 Jan, 2009
2 commits
-
They are actually alpha vs. i386/arm/m68k i.e. ecoff vs. aout.
In the only place where we actually tried to handle arm and i386/m68k in
different ways (START_DATA() in coredump handling), the arm variant
works for all of them (i386 and m68k have u.start_code set to 0).Signed-off-by: Al Viro
Signed-off-by: Linus Torvalds -
it's been used only in sunos compat
Signed-off-by: Al Viro
Signed-off-by: Linus Torvalds
14 Nov, 2008
1 commit
-
Make execve() take advantage of copy-on-write credentials, allowing it to set
up the credentials in advance, and then commit the whole lot after the point
of no return.This patch and the preceding patches have been tested with the LTP SELinux
testsuite.This patch makes several logical sets of alteration:
(1) execve().
The credential bits from struct linux_binprm are, for the most part,
replaced with a single credentials pointer (bprm->cred). This means that
all the creds can be calculated in advance and then applied at the point
of no return with no possibility of failure.I would like to replace bprm->cap_effective with:
cap_isclear(bprm->cap_effective)
but this seems impossible due to special behaviour for processes of pid 1
(they always retain their parent's capability masks where normally they'd
be changed - see cap_bprm_set_creds()).The following sequence of events now happens:
(a) At the start of do_execve, the current task's cred_exec_mutex is
locked to prevent PTRACE_ATTACH from obsoleting the calculation of
creds that we make.(a) prepare_exec_creds() is then called to make a copy of the current
task's credentials and prepare it. This copy is then assigned to
bprm->cred.This renders security_bprm_alloc() and security_bprm_free()
unnecessary, and so they've been removed.(b) The determination of unsafe execution is now performed immediately
after (a) rather than later on in the code. The result is stored in
bprm->unsafe for future reference.(c) prepare_binprm() is called, possibly multiple times.
(i) This applies the result of set[ug]id binaries to the new creds
attached to bprm->cred. Personality bit clearance is recorded,
but now deferred on the basis that the exec procedure may yet
fail.(ii) This then calls the new security_bprm_set_creds(). This should
calculate the new LSM and capability credentials into *bprm->cred.This folds together security_bprm_set() and parts of
security_bprm_apply_creds() (these two have been removed).
Anything that might fail must be done at this point.(iii) bprm->cred_prepared is set to 1.
bprm->cred_prepared is 0 on the first pass of the security
calculations, and 1 on all subsequent passes. This allows SELinux
in (ii) to base its calculations only on the initial script and
not on the interpreter.(d) flush_old_exec() is called to commit the task to execution. This
performs the following steps with regard to credentials:(i) Clear pdeath_signal and set dumpable on certain circumstances that
may not be covered by commit_creds().(ii) Clear any bits in current->personality that were deferred from
(c.i).(e) install_exec_creds() [compute_creds() as was] is called to install the
new credentials. This performs the following steps with regard to
credentials:(i) Calls security_bprm_committing_creds() to apply any security
requirements, such as flushing unauthorised files in SELinux, that
must be done before the credentials are changed.This is made up of bits of security_bprm_apply_creds() and
security_bprm_post_apply_creds(), both of which have been removed.
This function is not allowed to fail; anything that might fail
must have been done in (c.ii).(ii) Calls commit_creds() to apply the new credentials in a single
assignment (more or less). Possibly pdeath_signal and dumpable
should be part of struct creds.(iii) Unlocks the task's cred_replace_mutex, thus allowing
PTRACE_ATTACH to take place.(iv) Clears The bprm->cred pointer as the credentials it was holding
are now immutable.(v) Calls security_bprm_committed_creds() to apply any security
alterations that must be done after the creds have been changed.
SELinux uses this to flush signals and signal handlers.(f) If an error occurs before (d.i), bprm_free() will call abort_creds()
to destroy the proposed new credentials and will then unlock
cred_replace_mutex. No changes to the credentials will have been
made.(2) LSM interface.
A number of functions have been changed, added or removed:
(*) security_bprm_alloc(), ->bprm_alloc_security()
(*) security_bprm_free(), ->bprm_free_security()Removed in favour of preparing new credentials and modifying those.
(*) security_bprm_apply_creds(), ->bprm_apply_creds()
(*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()Removed; split between security_bprm_set_creds(),
security_bprm_committing_creds() and security_bprm_committed_creds().(*) security_bprm_set(), ->bprm_set_security()
Removed; folded into security_bprm_set_creds().
(*) security_bprm_set_creds(), ->bprm_set_creds()
New. The new credentials in bprm->creds should be checked and set up
as appropriate. bprm->cred_prepared is 0 on the first call, 1 on the
second and subsequent calls.(*) security_bprm_committing_creds(), ->bprm_committing_creds()
(*) security_bprm_committed_creds(), ->bprm_committed_creds()New. Apply the security effects of the new credentials. This
includes closing unauthorised files in SELinux. This function may not
fail. When the former is called, the creds haven't yet been applied
to the process; when the latter is called, they have.The former may access bprm->cred, the latter may not.
(3) SELinux.
SELinux has a number of changes, in addition to those to support the LSM
interface changes mentioned above:(a) The bprm_security_struct struct has been removed in favour of using
the credentials-under-construction approach.(c) flush_unauthorized_files() now takes a cred pointer and passes it on
to inode_has_perm(), file_has_perm() and dentry_open().Signed-off-by: David Howells
Acked-by: James Morris
Acked-by: Serge Hallyn
Signed-off-by: James Morris
27 Jul, 2008
1 commit
-
This moves all the ptrace hooks related to exec into tracehook.h inlines.
This also lifts the calls for tracing out of the binfmt load_binary hooks
into search_binary_handler() after it calls into the binfmt module. This
change has no effect, since all the binfmt modules' load_binary functions
did the call at the end on success, and now search_binary_handler() does
it immediately after return if successful. We consolidate the repeated
code, and binfmt modules no longer need to import ptrace_notify().Signed-off-by: Roland McGrath
Cc: Oleg Nesterov
Reviewed-by: Ingo Molnar
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
29 Apr, 2008
1 commit
-
Use printk_ratelimit() instead of jiffies based arithmetic, suggested by Geert
UytterhoevenSigned-off-by: S.Caglar Onur
Cc: Geert Uytterhoeven
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
09 Feb, 2008
1 commit
-
Suppress A.OUT library support if CONFIG_ARCH_SUPPORTS_AOUT is not set.
Not all architectures support the A.OUT binfmt, so the ELF binfmt should not
be permitted to go looking for A.OUT libraries to load in such a case. Not
only that, but under such conditions A.OUT core dumps are not produced either.To make this work, this patch also does the following:
(1) Makes the existence of the contents of linux/a.out.h contingent on
CONFIG_ARCH_SUPPORTS_AOUT.(2) Renames dump_thread() to aout_dump_thread() as it's only called by A.OUT
core dumping code.(3) Moves aout_dump_thread() into asm/a.out-core.h and makes it inline. This
is then included only where needed. This means that this bit of arch
code will be stored in the appropriate A.OUT binfmt module rather than
the core kernel.(4) Drops A.OUT support for Blackfin (according to Mike Frysinger it's not
needed) and FRV.This patch depends on the previous patch to move STACK_TOP[_MAX] out of
asm/a.out.h and into asm/processor.h as they're required whether or not A.OUT
format is available.[jdike@addtoit.com: uml: re-remove accidentally restored code]
Signed-off-by: David Howells
Cc:
Signed-off-by: Jeff Dike
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
08 Feb, 2008
1 commit
-
struct user.u_ar0 is defined to contain a pointer offset on all
architectures in which it is defined (all architectures which define an
a.out format except SPARC.) However, it has a pointer type in the headers,
which is pointless -- is not exported to userspace, and it
just makes the code messy.Redefine the field as "unsigned long" (which is the same size as a pointer
on all Linux architectures) and change the setting code to user offsetof()
instead of hand-coded arithmetic.Cc: Linux Arch Mailing List
Cc: Bryan Wu
Cc: Roman Zippel
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: Richard Henderson
Cc: Ivan Kokshaysky
Cc: Russell King
Cc: Lennert Buytenhek
Cc: Håvard Skinnemoen
Cc: Mikael Starvik
Cc: Yoshinori Sato
Cc: Tony Luck
Cc: Hirokazu Takata
Cc: Ralf Baechle
Cc: Paul Mackerras
Cc: Martin Schwidefsky
Cc: Heiko Carstens
Cc: Paul Mundt
Signed-off-by: H. Peter Anvin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
20 Dec, 2007
1 commit
-
The problem was introduced by commit "mm: variable length argument
support" (b6a2fea39318e43fee84fa7b0b90d68bed92d2ba)
as it didn't update fs/binfmt_aout.c like other binfmt's.I noticed that on alpha when accidentally launched old OSF/1
Acrobat Reader binary. Obviously, other architectures are affected
as well.Signed-off-by: Ivan Kokshaysky
Cc: Ollie Wild
Acked-by: Peter Zijlstra
Cc: Andrew Morton
Cc: Hugh Dickins
Cc: Adrian Bunk
Signed-off-by: Linus Torvalds
17 Oct, 2007
1 commit
-
For some time /proc/sys/kernel/core_pattern has been able to set its output
destination as a pipe, allowing a user space helper to receive and
intellegently process a core. This infrastructure however has some
shortcommings which can be enhanced. Specifically:1) The coredump code in the kernel should ignore RLIMIT_CORE limitation
when core_pattern is a pipe, since file system resources are not being
consumed in this case, unless the user application wishes to save the core,
at which point the app is restricted by usual file system limits and
restrictions.2) The core_pattern code should be able to parse and pass options to the
user space helper as an argv array. The real core limit of the uid of the
crashing proces should also be passable to the user space helper (since it
is overridden to zero when called).3) Some miscellaneous bugs need to be cleaned up (specifically the
recognition of a recursive core dump, should the user mode helper itself
crash. Also, the core dump code in the kernel should not wait for the user
mode helper to exit, since the same context is responsible for writing to
the pipe, and a read of the pipe by the user mode helper will result in a
deadlock.This patch:
Remove the check of RLIMIT_CORE if core_pattern is a pipe. In the event that
core_pattern is a pipe, the entire core will be fed to the user mode helper.Signed-off-by: Neil Horman
Cc:
Cc:
Cc: Jeremy Fitzhardinge
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
09 Dec, 2006
1 commit
-
This patch changes struct file to use struct path instead of having
independent pointers to struct dentry and struct vfsmount, and converts all
users of f_{dentry,vfsmnt} in fs/ to use f_path.{dentry,mnt}.Additionally, it adds two #define's to make the transition easier for users of
the f_dentry and f_vfsmnt.Signed-off-by: Josef "Jeff" Sipek
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
30 Sep, 2006
1 commit
-
Files supported by fs/proc/base.c, i.e. /proc//*, are not capable of
meeting the validity checks in ELF load_elf_*() handling because they have
no mmap handler which is required by ELF. In order to stop a.out
executables being used as part of an exploit attack against /proc-related
vulnerabilities, we make a.out executables depend on ->mmap() existing.Signed-off-by: Eugene Teo
Signed-off-by: Marcel Holtmann
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
11 Jan, 2006
1 commit
-
)
From: Adrian Bunk
- create one common dump_thread() prototype in kernel.h
- dump_thread() is only used in fs/binfmt_aout.c and can therefore be
removed on all architectures where CONFIG_BINFMT_AOUT is not
availableSigned-off-by: Adrian Bunk
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
30 Oct, 2005
1 commit
-
How is anon_rss initialized? In dup_mmap, and by mm_alloc's memset; but
that's not so good if an mm_counter_t is a special type. And how is rss
initialized? By set_mm_counter, all over the place. Come on, we just need to
initialize them both at once by set_mm_counter in mm_init (which follows the
memcpy when forking).Signed-off-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
22 Jun, 2005
1 commit
-
Ingo recently introduced a great speedup for allocating new mmaps using the
free_area_cache pointer which boosts the specweb SSL benchmark by 4-5% and
causes huge performance increases in thread creation.The downside of this patch is that it does lead to fragmentation in the
mmap-ed areas (visible via /proc/self/maps), such that some applications
that work fine under 2.4 kernels quickly run out of memory on any 2.6
kernel.The problem is twofold:
1) the free_area_cache is used to continue a search for memory where
the last search ended. Before the change new areas were always
searched from the base address on.So now new small areas are cluttering holes of all sizes
throughout the whole mmap-able region whereas before small holes
tended to close holes near the base leaving holes far from the base
large and available for larger requests.2) the free_area_cache also is set to the location of the last
munmap-ed area so in scenarios where we allocate e.g. five regions of
1K each, then free regions 4 2 3 in this order the next request for 1K
will be placed in the position of the old region 3, whereas before we
appended it to the still active region 1, placing it at the location
of the old region 2. Before we had 1 free region of 2K, now we only
get two free regions of 1K -> fragmentation.The patch addresses thes issues by introducing yet another cache descriptor
cached_hole_size that contains the largest known hole size below the
current free_area_cache. If a new request comes in the size is compared
against the cached_hole_size and if the request can be filled with a hole
below free_area_cache the search is started from the base instead.The results look promising: Whereas 2.6.12-rc4 fragments quickly and my
(earlier posted) leakme.c test program terminates after 50000+ iterations
with 96 distinct and fragmented maps in /proc/self/maps it performs nicely
(as expected) with thread creation, Ingo's test_str02 with 20000 threads
requires 0.7s system time.Taking out Ingo's patch (un-patch available per request) by basically
deleting all mentions of free_area_cache from the kernel and starting the
search for new memory always at the respective bases we observe: leakme
terminates successfully with 11 distinctive hardly fragmented areas in
/proc/self/maps but thread creating is gringdingly slow: 30+s(!) system
time for Ingo's test_str02 with 20000 threads.Now - drumroll ;-) the appended patch works fine with leakme: it ends with
only 7 distinct areas in /proc/self/maps and also thread creation seems
sufficiently fast with 0.71s for 20000 threads.Signed-off-by: Wolfgang Wander
Credit-to: "Richard Purdie"
Signed-off-by: Ken Chen
Acked-by: Ingo Molnar (partly)
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
17 Apr, 2005
1 commit
-
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!
