Commit Graph

4 Commits

Author SHA1 Message Date
Kostya Kortchinsky 419f1a4185 [scudo][standalone] Optimization pass
Summary:
This introduces a bunch of small optimizations with the purpose of
making the fastpath tighter:
- tag more conditions as `LIKELY`/`UNLIKELY`: as a rule of thumb we
  consider that every operation related to the secondary is unlikely
- attempt to reduce the number of potentially extraneous instructions
- reorganize the `Chunk` header to not straddle a word boundary and
  use more appropriate types

Note that some `LIKELY`/`UNLIKELY` impact might be less obvious as
they are in slow paths (for example in `secondary.cc`), but at this
point I am throwing a pretty wide net, and it's consistant and doesn't
hurt.

This was mosly done for the benfit of Android, but other platforms
benefit from it too. An aarch64 Android benchmark gives:
- before:
```
  BM_youtube/min_time:15.000/repeats:4/manual_time_mean              445244 us       659385 us            4
  BM_youtube/min_time:15.000/repeats:4/manual_time_median            445007 us       658970 us            4
  BM_youtube/min_time:15.000/repeats:4/manual_time_stddev               885 us         1332 us            4
```
- after:
```
  BM_youtube/min_time:15.000/repeats:4/manual_time_mean       415697 us       621925 us            4
  BM_youtube/min_time:15.000/repeats:4/manual_time_median     415913 us       622061 us            4
  BM_youtube/min_time:15.000/repeats:4/manual_time_stddev        990 us         1163 us            4
```

Additional since `-Werror=conversion` is enabled on some platforms we
are built on, enable it upstream to catch things early: a few sign
conversions had slept through and needed additional casting.

Reviewers: hctim, morehouse, eugenis, vitalybuka

Reviewed By: vitalybuka

Subscribers: srhines, mgorny, javed.absar, kristof.beyls, delcypher, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D64664

llvm-svn: 366918
2019-07-24 16:36:01 +00:00
Kostya Kortchinsky aeb3826228 [scudo][standalone] Merge Spin & Blocking mutex into a Hybrid one
Summary:
We ran into a problem on Fuchsia where yielding threads would never
be deboosted, ultimately resulting in several threads spinning on the
same TSD, and no possibility for another thread to be scheduled,
dead-locking the process.

While this was fixed in Zircon, this lead to discussions about if
spinning without a break condition was a good decision, and settled on
a new hybrid model that would spin for a while then block.

Currently we are using a number of iterations for spinning that is
mostly arbitrary (based on sanitizer_common values), but this can
be tuned in the future.

Since we are touching `common.h`, we also use this change as a vehicle
for an Android optimization (the page size is fixed in Bionic, so use
a fixed value too).

Reviewers: morehouse, hctim, eugenis, dvyukov, vitalybuka

Reviewed By: hctim

Subscribers: srhines, delcypher, jfb, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D64358

llvm-svn: 365790
2019-07-11 15:32:26 +00:00
Kostya Kortchinsky 624a24e156 [scudo][standalone] Unmap memory in tests
Summary:
The more tests are added, the more we are limited by the size of the
address space on 32-bit. Implement `unmapTestOnly` all around (like it
is in sanitzer_common) to be able to free up some memory.
This is not intended to be a proper "destructor" for an allocator, but
allows us to not fail due to having no memory left.

Reviewers: morehouse, vitalybuka, eugenis, hctim

Reviewed By: morehouse

Subscribers: delcypher, jfb, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D63146

llvm-svn: 363095
2019-06-11 19:50:12 +00:00
Kostya Kortchinsky 52bfd673d1 [scudo][standalone] Introduce the thread specific data structures
Summary:
This CL adds the structures dealing with thread specific data for the
allocator. This includes the thread specific data structure itself and
two registries for said structures: an exclusive one, where each thread
will have its own TSD struct, and a shared one, where a pool of TSD
structs will be shared by all threads, with dynamic reassignment at
runtime based on contention.

This departs from the current Scudo implementation: we intend to make
the Registry a template parameter of the allocator (as opposed to a
single global entity), allowing various allocators to coexist with
different TSD registry models. As a result, TSD registry and Allocator
are tightly coupled.

This also corrects a couple of things in other files that I noticed
while adding this.

Reviewers: eugenis, vitalybuka, morehouse, hctim

Reviewed By: morehouse

Subscribers: srhines, mgorny, delcypher, jfb, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D62258

llvm-svn: 362962
2019-06-10 16:50:52 +00:00