А померяемся make.conf

#lto-overlay
NTHREADS="3"
source /etc/portage/make.conf.lto
COMMON_FLAGS="-march=native ${CFLAGS} -pipe"
CFLAGS="${COMMON_FLAGS}"
CXXFLAGS="${COMMON_FLAGS}"
FCFLAGS="${COMMON_FLAGS}"
FFLAGS="${COMMON_FLAGS}"

PORTDIR="/var/db/repos/gentoo"
DISTDIR="/var/cache/distfiles"
PKGDIR="/var/cache/binpkgs"

MAKEOPTS="-j3"
LC_MESSAGES=C

CPU_FLAGS_X86="mmx mmxext sse sse2 sse3 ssse3"
VIDEO_CARDS="intel i915"
LLVM_TARGETS="X86"
USE_ADD="threads jemalloc clang lto graphite pulseaudio alsa nls"
USE_DEL="-ipv6 -smartcard -bluetooth -doc -cdda -dvd -ccache"
USE="${USE_ADD} ${USE_DEL}"
LINGUAS="en ru"
L10N="en ru"


EMERGE_DEFAULT_OPTS="--jobs 3 --load-average 4.9"
PORTAGE_LOGDIR="/var/log/portage/"
FEATURES="${FEATURES} downgrade-backup fail-clean nodoc parallel-fetch parallel-install"
PORTAGE_NICENESS="15"
ACCEPT_LICENSE="*"
CMAKE_MAKEFILE_GENERATOR="ninja"

CFLAGS="-O2 -pipe -march=native"
CXXFLAGS="${CFLAGS}"

CHOST="x86_64-pc-linux-gnu"

CPU_FLAGS_X86="aes avx avx2 f16c fma3 mmx mmxext popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3"

PKGDIR="${PORTDIR}/packages"

GUIFRAMEWORKS="-gnome -gtk3 -gtk2 -gtk -qt4 qt5 -qt3support"
ENV="acpi bash-completion elogind policykit  dbus threads unicode utf8 icu usb mime threads"
_ENV="-cdr -debug -consolekit -evdev"
FONTS="fontconfig truetype cleartype corefonts"
VIDEOCODECS="theora mp4 mpeg ogv ffmpeg vdpau vaapi"
AUDIOCODECS="aac mp3 vorbis ogg gstreamer alsa"
IMG="jpeg gphoto2"
TXT="djvu pdf spell"
NETCFG="ipv6 -cups bluetooth wifi"
POTTERINGSHIT="pulseaudio -systemd"
DEV="usb lm_sensors fuse udisks"
KERNELOPT="symlink"
XORG="xinerama libglvnd"

USE="sqlite fam $GUIFRAMEWORKS $ENV $_ENV $FONTS $VIDEOCODECS $AUDIOCODECS $IMG $TXT $NETCFG $POTTERINGSHIT $DEV $KERNELOPT $XORG"

VIDEO_CARDS="nvidia vesa"
CAMERAS="canon"
ALSA_CARDS="hda-intel"

INPUT_DEVICES="libinput"
MAKEOPTS="-j8 -l6"


EMERGE_DEFAULT_OPTS="--autounmask=n --jobs 9 --load-average=9 --keep-going=y"
#EMERGE_DEFAULT_OPTS="--autounmask=n --jobs 9"
PORTAGE_IONICE_COMMAND="ionice -c 3 -p \${PID}"
PORTAGE_NICENESS=-10

ACCEPT_LICENSE="*"
LINGUAS="en ru"
L10N="en-GB ru"

PORTAGE_TMPDIR="/tmp"
FEATURES="${FEATURES} parallel-fetch"

ABI_X86="64 32"
#PYTHON_TARGETS="python3_8"
#PYTHON_SINGLE_TARGET="python3_8"

RUBY_TARGETS="ruby26 ruby27 ruby30"

#INSTALL_MASK="/usr/shared/alsa/alsa.conf.d/*"
#PORTDIR_OVERLAY="/usr/local/portage $PORTDIR_OVERLAY"

ACCEPT_KEYWORDS="~amd64"

LTO="-flto"
CFLAGS="-O2 -march=sandybridge -mno-avx -mno-xsave -mno-xsaveopt -mfpmath=both -pipe -fomit-frame-pointer -ftree-vectorize -fvect-cost-model=cheap ${LTO}"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-O2 -Wl,--as-needed -Wl,-z,relro,-z,now ${LTO}"
CPU_FLAGS_X86="mmx mmxext popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3"
DISTDIR="/var/lib/portage/distfiles"
PKGDIR="/var/lib/portage/packages"
EMERGE_DEFAULT_OPTS="--verbose --ask=y --ask-enter-invalid --ignore-built-slot-operator-deps=y --usepkg --autounmask-keep-masks"
FEATURES="candy cgroup clean-logs compress-build-logs -ebuild-locks parallel-install metadata-transfer multilib-strict network-sandbox parallel-fetch preserve-libs protect-owned strict sfperms userfetch userpriv usersandbox usersync"
FFTOOLS=""
INPUT_DEVICES="libinput"
ACCEPT_KEYWORDS="~amd64"
L10N="en-GB en ru"
LLVM_TARGETS=""
GCC_PATH="/usr/x86_64-pc-linux-gnu/gcc-bin/10.3.0"
AR="${GCC_PATH}/gcc-ar"
NM="${GCC_PATH}/gcc-nm"
RANLIB="${GCC_PATH}/gcc-ranlib"
MAKEOPTS="-j3"
MICROCODE_SIGNATURES="-S"
PORTAGE_NICENESS=10
PORTAGE_IONICE_COMMAND="ionice -c 3 -p \${PID}"
PYTHON_TARGETS="python3_9"
PYTHON_SINGLE_TARGET="python3_9"
RUBY_TARGETS="ruby30"
PORTAGE_TMPDIR="/tmp"
USE="
egl
gtk
gtk3
vaapi
luajit
wayland
zsh-completion
vim-syntax
idn
libidn2
pch
jit
ffmpeg
fontconfig
gnome-keyring
gstreamer
pulseaudio
pwquality
theora
icu
libass
lto
lz4
openssl
opus
pgo
threads
v4l
vpx
webp
zstd
-gtk2
-qt
-qt4
-qt5
-kde
-cups
-python
-passwdqc
-vdpau
-wxwidgets
-ldap
-berkdb
-xattr
-perl
-cdda
-gnutls
-upnp
-networkmanager
-split-usr
-suid
"
VIDEO_CARDS="intel nvidia"