tree 7fdf43651a8effc80b4735b65275763db76c687a
parent 99c763a30609281a6e83a1c4bc3430d3c84d5e54
author Evgeniy Stepanov <eugeni.stepanov@gmail.com> 1547862849 +0000
committer Pirama Arumuga Nainar <pirama@google.com> 1548434581 -0800

[hwasan] Madvise away unused shadow.

Summary:
Whenever a large shadow region is tagged to zero, madvise(DONT_NEED)
as much of it as possible.

This reduces shadow RSS on Android by 45% or so, and total memory use
by 2-4%, probably even more on long running multithreaded programs.
CPU time seems to be in the noise.

Reviewers: kcc, pcc

Subscribers: srhines, kubamracek, llvm-commits

Differential Revision: https://reviews.llvm.org/D56757

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@351620 91177308-0d34-0410-b5e6-96231b3b80d8