The algorithm puts elements into correct positions in multiple iterations.
On the first iteration it tries to put elements at entries specified by
their first hash probe. On the second iteration -- by the second
hash probe, and so on. Overall it does O(k*n) memory accesses, where
k is the maximum number of probes required for an element and n is the
capacity of the hash table. The expectation is that k will be small.
R=mstarzinger@chromium.org
Review URL: https://chromiumcodereview.appspot.com/23658031
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16678 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This change is mostly straightforward: for 'normal' sorts of change records,
simply don't deliver a changeRecord to a given observer callback if an access
the callback's Context is not allowed to "GET" or "HAS" changeRecord.name on
changeRecord.object, or if ACCESS_KEYS is disallowed.
For 'splice' records, the question of whether to hand it to an observer is trickier, since
there are multiple properties involved, and multiple types of possible information leakage.
Given that access-checked objects are very rare (only two in Blink, Window and Location),
and that they are not normally used as Arrays, it seems better to simply not emit any splice
records for such objects rather than spending lots of logic to attempt to avoid information
leakage for something that may never happen.
BUG=v8:2778
R=rossberg@chromium.org
Review URL: https://codereview.chromium.org/22962009
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16663 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Original descriptions were:
- "Refactor and cleanup VirtualMemory."
- "Fix typo."
- "Deuglify V8_INLINE and V8_NOINLINE."
- "Don't align size on allocation granularity for unaligned ReserveRegion calls."
Reasons for the revert are:
- Our mjsunit test suite slower by a factor of 5(!) in release mode.
- Flaky cctest/test-alloc/CodeRange on all architectures and platforms.
- Tankage of Sunspider by about 6% overall (unverified).
TBR=bmeurer@chromium.org
Review URL: https://codereview.chromium.org/23970004
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16662 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Remove a lot of platform duplication, and simplify the virtual
memory implementation. Also improve readability by avoiding bool
parameters for executability (use a dedicated Executability type
instead).
Get rid of the Isolate::UncheckedCurrent() call in the platform
code, as part of the Isolate TLS cleanup.
Use a dedicated random number generator for the address
randomization, instead of messing with the per-isolate random
number generators.
TEST=cctest/test-virtual-memory
R=verwaest@chromium.org
Review URL: https://codereview.chromium.org/23641009
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16637 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Observation in the normal case (Object.observe, default accept types, one observer) now allocates fewer objects and unobservation no longer needs to scan and splice an InternalArray -- making the combined speed of observe/unobserve about 200% faster.
This patch implements the following optimizations:
-objectInfo is initially created without any connected objects or arrays. The first observer is referenced directly by objectInfo, and when a second observer is added, changeObservers converts to a mapping of callbackPriority->observer, which allows for constant time registration/de-registration.
-observer.accept and objectInfo.performing are conceptually the same data-structure. This is now directly represented as an abstract "TypeMap" which can later be optimized to be a smi in common cases, (e.g: https://codereview.chromium.org/19269007/).
-objectInfo observers are only represented by an object with an accept typeMap if the set of accept types is non-default
R=rossberg@chromium.org
Review URL: https://codereview.chromium.org/19541010
Patch from Rafael Weinstein <rafaelw@chromium.org>.
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16629 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The RandomNumberGenerator is a pseudorandom number generator
with 48-bit state. It is properly seeded using either
(1) the --random-seed if specified, or
(2) the entropy_source function if configured, or
(3) /dev/urandom if available, or
(4) falls back to Time and TimeTicks based seeding.
Each Isolate now contains a RandomNumberGenerator, which replaces
the previous private_random_seed.
Every native context still has its own random_seed. But this random
seed is now properly initialized during bootstrapping,
instead of on-demand initialization. This will allow us to cleanup
and speedup the HRandom implementation quite a lot (this is delayed
for a followup CL)!
Also stop messing with the system rand()/random(), which should
not be done from a library anyway! We probably re-seeded the
libc rand()/random() after the application (i.e. Chrome) already
seeded it (with better entropy than what we used).
Another followup CL will replace the use of the per-isolate
random number generator for the address randomization and
thereby get rid of the Isolate::UncheckedCurrent() usage in
the platform code.
TEST=cctest/test-random-number-generator,cctest/test-random
R=mstarzinger@chromium.org
Review URL: https://codereview.chromium.org/23548024
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16612 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The reason of that is a number of cons strings in the app.
The app constructs a json string and as a result v8 heap has
a very long chain of cons strings.
Profiler counts all these strings as plain String objects and
assign the content of the strings as node names.
It required O(n^2) time and O(n^2) memory.
Solution: I introduced two new types, kConsString and kSliced string.
They do not use the content of the string for names. So the problem disappeared.
The heap profiler usability problem will be solved on Blink side.
BUG=285770
R=yangguo@chromium.org
Review URL: https://codereview.chromium.org/23460027
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16611 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Current v8 implementation may disable optimization for a particular function or block it with help of dont_optimize flag.
The patch propagates the reason of that to the SharedFunctionInfo where cpu profiler can get it.
SharedFunctionInfo is a heap object so I extracted 8 bits from OptsCount for handling bailout reason code.
BUG=none
TEST=test-profile-generator/BailoutReason
R=yangguo@chromium.org
Review URL: https://codereview.chromium.org/23817003
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16555 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Instead of globally tracking allocated space limits, which was
not implemented properly anyway (i.e. lack of synchronization
on the reading side), track it per MemoryAllocator (that is
per heap/isolate).
In particular, avoid to call IsBadWritePtr() on Windows, it is
obsolete and Microsoft strongly discourages its usage.
R=mstarzinger@chromium.org
Review URL: https://codereview.chromium.org/23903008
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16542 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Observation in the normal case (Object.observe, default accept types, one observer) now allocates fewer objects and unobservation no longer needs to scan and splice an InternalArray -- making the combined speed of observe/unobserve about 200% faster.
This patch implements the following optimizations:
-objectInfo is initially created without any connected objects or arrays. The first observer is referenced directly by objectInfo, and when a second observer is added, changeObservers converts to a mapping of callbackPriority->observer, which allows for constant time registration/de-registration.
-observer.accept and objectInfo.performing are conceptually the same data-structure. This is now directly represented as an abstract "TypeMap" which can later be optimized to be a smi in common cases, (e.g: https://codereview.chromium.org/19269007/).
-objectInfo observers are only represented by an object with an accept typeMap if the set of accept types is non-default
R=rossberg@chromium.org
Committed: https://code.google.com/p/v8/source/detail?r=16343
Review URL: https://codereview.chromium.org/19541010
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16539 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Condition variables are synchronization primitives that can be used
to block one or more threads while waiting for condition to become
true.
Right now we have only semaphores, mutexes and atomic operations for
synchronization, which results in quite complex solutions where an
implementation using condition variables and mutexes would be straight
forward.
There's also a performance benefit to condition variables and mutexes
vs semaphores, especially on Windows, where semaphores are kernel
objects, while mutexes are implemented as fast critical sections,
it CAN be beneficial performance-wise to use condition variables
instead of semaphores.
R=mstarzinger@chromium.org
Review URL: https://codereview.chromium.org/23548007
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16492 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Drop the previous Mutex and ScopedLock classes from platform files.
Add new Mutex, RecursiveMutex and LockGuard classes, which are
designed after their C++11 counterparts, so that at some point
we can simply drop our custom code and switch to the C++11
classes. We distinguish regular and recursive mutexes, as the
latter don't work well with condition variables, which will be
introduced by a followup CL.
R=mstarzinger@chromium.org
Review URL: https://codereview.chromium.org/23625003
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16416 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
These classes are meant to replace OS::Ticks() and OS::TimeCurrentMillis(),
which are broken in several ways. The ElapsedTimer class implements a
stopwatch using TimeTicks::HighResNow() for high resolution, monotonic
timing.
Also fix the CpuProfile::GetStartTime() and CpuProfile::GetEndTime()
methods to actually return the time relative to the unix epoch as stated
in the documentation (previously that was relative to some arbitrary
point in time, i.e. boot time).
The previous Windows issues have been resolved, and we now use GetTickCount64()
on Windows Vista and later, falling back to timeGetTime() with rollover
protection for earlier Windows versions.
BUG=v8:2853
R=machenbach@chromium.org, yurys@chromium.org
Review URL: https://codereview.chromium.org/23490015
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16413 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
These classes are meant to replace OS::Ticks() and OS::TimeCurrentMillis(),
which are broken in several ways. The ElapsedTimer class implements a
stopwatch using TimeTicks::HighResNow() for high resolution, monotonic
timing.
Also fix the CpuProfile::GetStartTime() and CpuProfile::GetEndTime()
methods to actually return the time relative to the unix epoch as stated
in the documentation (previously that was relative to some arbitrary
point in time, i.e. boot time).
BUG=v8:2853
R=machenbach@chromium.org
Review URL: https://codereview.chromium.org/23469013
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16398 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
