commit 466e0ecb88a5cbdd0528ff22e81fa7c028ee9799
author Tim Murray <timmurray@google.com> Tue Jan 08 11:01:18 2019 -0800
committer Tim Murray <timmurray@google.com> Tue Jan 08 13:27:41 2019 -0800
tree 30b39f313e493754173eabb9667153b53ad9de3c
parent 5d89fbd207ce5ab09c6ae54193d82b8495c839c5

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

libc/bionic/pthread_create.cpp

diff --git a/libc/bionic/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index 8e8d180..06d2ecb 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -76,8 +76,6 @@
     return nullptr;
   }
 
-  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, allocation, allocation_size, "bionic TLS guard");
-
   // Carve out the writable TLS section.
   bionic_tls* result = reinterpret_cast<bionic_tls*>(static_cast<char*>(allocation) +
                                                      PTHREAD_GUARD_SIZE);
@@ -88,7 +86,6 @@
     return nullptr;
   }
 
-  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, result, BIONIC_TLS_SIZE, "bionic TLS");
   return result;
 }
 
@@ -111,7 +108,6 @@
     // 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");
   }
 }
 
@@ -214,8 +210,6 @@
     munmap(space, mmap_size);
     return nullptr;
   }
-  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, space, stack_guard_size, "thread stack guard");
-
   return space;
 }