commit 973b64c3e55be7f8e14cece946b0c726a31ef2b4
author Tim Murray <timmurray@google.com> Tue Jan 08 11:01:18 2019 -0800
committer android-build-team Robot <android-build-team-robot@google.com> Thu Jan 17 21:08:20 2019 +0000
tree a8a6930da3fad04ed79054576abfbb0c3980e033
parent b32be3f072132a2833e5ab963ce4a2592436805f

Remove some PR_SET_VMAs during pthread_create

PR_SET_VMA takes mmap_sem, which can cause contention and reduce
performance any time many threads are created at the same time,
like app startup.

Test: camera launch performance
Bug: 122471935
Change-Id: If7fa7ad99654c01d503f694976fd92bfd30d2afd
Merged-in: If7fa7ad99654c01d503f694976fd92bfd30d2afd
(cherry picked from commit dad73ef232034dd0f4f46bda90c74e8727d840cc)

libc/bionic/pthread_create.cpp

diff --git a/libc/bionic/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index 21a707b..8825c6f 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -65,8 +65,6 @@
     return false;
   }
 
-  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, allocation, allocation_size, "bionic TLS guard");
-
   // Carve out the writable TLS section.
   thread->bionic_tls = reinterpret_cast<bionic_tls*>(static_cast<char*>(allocation) +
                                                      PTHREAD_GUARD_SIZE);
@@ -77,7 +75,6 @@
     return false;
   }
 
-  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, thread->bionic_tls, BIONIC_TLS_SIZE, "bionic TLS");
   return true;
 }
 
@@ -105,7 +102,6 @@
     // We can only use const static allocated string for mapped region name, as Android kernel
     // uses the string pointer directly when dumping /proc/pid/maps.
     prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, ss.ss_sp, ss.ss_size, "thread signal stack");
-    prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, stack_base, PTHREAD_GUARD_SIZE, "thread signal stack guard");
   }
 }
 
@@ -184,8 +180,6 @@
     munmap(space, mmap_size);
     return NULL;
   }
-  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, space, stack_guard_size, "thread stack guard");
-
   return space;
 }