On Thu, Jul 28, 2022 at 05:09:38PM -0400, Jeff King wrote:
> > Ditto TEST_NO_MALLOC_CHECK=1 & --no-bin-wrappers, but we can think about
> > all of those some other time....
>
> I'd be surprised if the malloc checking itself is all that expensive,
> though it does look like we call getconf and expr once per test there
> for setup. We could almost certainly hoist that out and call it once per
> script.
Nope, I was totally wrong here. Running with TEST_NO_MALLOC_CHECK=1 does
indeed make a big difference:
Benchmark 1: make test
Time (mean ± σ): 67.486 s ± 3.339 s [User: 622.643 s, System: 409.951 s]
Range (min … max): 63.634 s … 69.550 s 3 runs
Benchmark 2: TEST_NO_MALLOC_CHECK=1 make test
Time (mean ± σ): 57.596 s ± 0.899 s [User: 577.273 s, System: 291.627 s]
Range (min … max): 57.072 s … 58.634 s 3 runs
Eliminating the extra per-test processes with the patch below helps a
little, but most of the effort really is (presumably) going to the
actual malloc checking code:
Benchmark 1: make test [nb: after applying patch...]
Time (mean ± σ): 67.091 s ± 0.385 s [User: 599.382 s, System: 410.781 s]
Range (min … max): 66.648 s … 67.343 s 3 runs
Curious that most of the CPU time seems to go into system time. I'd have
thought it was extra internal malloc debugging bits, but maybe it is
allocating mmap/brk calls in a less efficient way. I dunno how any of it
actually works.
-Peff
---
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 55857af601..303fbe8ecc 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -557,14 +557,20 @@ then
: nothing
}
else
+ if _GLIBC_VERSION=$(getconf GNU_LIBC_VERSION 2>/dev/null) &&
+ _GLIBC_VERSION=${_GLIBC_VERSION#"glibc "} &&
+ expr 2.34 \<= "$_GLIBC_VERSION" >/dev/null
+ then
+ USE_LIBC_MALLOC_DEBUG=t
+ else
+ USE_LIBC_MALLOC_DEBUG=
+ fi
setup_malloc_check () {
local g
local t
MALLOC_CHECK_=3 MALLOC_PERTURB_=165
export MALLOC_CHECK_ MALLOC_PERTURB_
- if _GLIBC_VERSION=$(getconf GNU_LIBC_VERSION 2>/dev/null) &&
- _GLIBC_VERSION=${_GLIBC_VERSION#"glibc "} &&
- expr 2.34 \<= "$_GLIBC_VERSION" >/dev/null
+ if test -n "$USE_LIBC_MALLOC_DEBUG"
then
g=
LD_PRELOAD="libc_malloc_debug.so.0"
