# Mixing two runtimes

Threading Building Blocks (TBB) and oneAPI Threading Building Blocks (oneTBB) can be safely used in the same application. TBB and oneTBB runtimes are named differently and can be loaded safely within the same process. In addition, the ABI versioning is completely different that prevents symbols conflicts.

However, if both runtimes are loaded into the same process it can lead to oversubscription because each runtime will use its own pool of threads. It might lead to a performance penalty due to increased number of context switches. To check if both TBB and oneTBB are loaded to the application, export `TBB_VERSION=1` before the application run. If both runtimes are loaded there will be two blocks of output, for example:

oneTBB possible output:

    oneTBB: SPECIFICATION VERSION       1.0
    oneTBB: VERSION             2021.2
    oneTBB: INTERFACE VERSION   12020
    oneTBB: TBB_USE_DEBUG       1
    oneTBB: TBB_USE_ASSERT      1
    oneTBB: TOOLS SUPPORT       disabled

TBB possible output:

    TBB: VERSION                2018.0
    TBB: INTERFACE VERSION      10006
    TBB: BUILD_DATE             Mon 01 Mar 2021 01:28:40 PM UTC
    TBB: BUILD_HOST             localhost (x86_64)
    TBB: BUILD_OS               Fedora release 32 (Thirty Two)
    TBB: BUILD_KERNEL   Linux 5.8.9-200.fc32.x86_64 #1 SMP Mon Sep 14 18:28:45 UTC 2020
    TBB: BUILD_GCC              g++ (GCC) 10.2.1 20201125 (Red Hat 10.2.1-9)
    TBB: BUILD_LIBC     2.31
    TBB: BUILD_LD               GNU ld version 2.34-6.fc32
    TBB: BUILD_TARGET   intel64 on cc10_libc2.31_kernel5.8.9
    TBB: BUILD_COMMAND  g++ -DDO_ITT_NOTIFY -g -O2 -DUSE_PTHREAD -m64 -fPIC -D__TBB_BUILD=1 -Wall -Wno-parentheses -Wno-non-virtual-dtor -I../../src -I../../src/rml/include -I../../include -I.
    TBB: TBB_USE_DEBUG  0
    TBB: TBB_USE_ASSERT 0
    TBB: DO_ITT_NOTIFY  1
    TBB: RML    private
    TBB: Tools support  disabled

Note

The `tbbmalloc` library in oneTBB is fully binary compatible with TBB.