diff --git a/deps/checksums/libuv b/deps/checksums/libuv
index c2c86a9767463..6887c3fe62f41 100644
--- a/deps/checksums/libuv
+++ b/deps/checksums/libuv
@@ -1,34 +1,34 @@
-LibUV.v2.0.1+17.aarch64-apple-darwin.tar.gz/md5/f176c76e5e2096dea8443302cf9550b8
-LibUV.v2.0.1+17.aarch64-apple-darwin.tar.gz/sha512/4301b13953a08a758b86e30af3261fd9a291ce3829b4d98e71e2a2c040e322e284c5a6eb4bc7189cc352f4b1cf7041e2cfd3380d511d88c151df3101ad74594e
-LibUV.v2.0.1+17.aarch64-linux-gnu.tar.gz/md5/c81515783363702a1bd4b65fd6d7f36b
-LibUV.v2.0.1+17.aarch64-linux-gnu.tar.gz/sha512/011429365337f5a45e56ca7a42709866bb994c747a1170d870f5f3ddfff2d36138866ee9278ac01172bc71bde8dee404bcb9cae9c7b44222bf1cc883659df269
-LibUV.v2.0.1+17.aarch64-linux-musl.tar.gz/md5/e74d5ea4912dd326b2705638faa7b805
-LibUV.v2.0.1+17.aarch64-linux-musl.tar.gz/sha512/a26a9f2c9051816230324071c502321f7af3885d581a400615858a93a4cd457226048d15b0e7f6a73d12659763c705b5ab519e9f5b35c6d886b9fd5babbfe352
-LibUV.v2.0.1+17.armv6l-linux-gnueabihf.tar.gz/md5/6df38bcf5d0a61dee63d16b73d0c9a24
-LibUV.v2.0.1+17.armv6l-linux-gnueabihf.tar.gz/sha512/d5354a6532061de0a58965ce0e427bde52f9ae0ee39a98e1a33de4c414fddcba9ba139ddf91be7321a4ccc97bbf7a8a8357ff10cf60f83c0a6bff7d839d6d7a8
-LibUV.v2.0.1+17.armv6l-linux-musleabihf.tar.gz/md5/6f02a24cfbfae3032fadceaea1faed39
-LibUV.v2.0.1+17.armv6l-linux-musleabihf.tar.gz/sha512/7fd107eb9a5ea84b488ea02e4fbedc9fe13bb11be859986a47af38f40ad775dd9f738c790878a3503437bcac1eb26ad9fe26f4aa0d3cb45c980b4c5abc9aec99
-LibUV.v2.0.1+17.armv7l-linux-gnueabihf.tar.gz/md5/96b09dec72f7e9b7409fa2920e67c866
-LibUV.v2.0.1+17.armv7l-linux-gnueabihf.tar.gz/sha512/6a0f79fc15c944fabba5c65180b665bc9769c6ff25863e330049f48b3a4394b448492f5a9a76bb7f8dbd3ce44dfc6f9ccdc2c71c42e1c749e88070fe99b1db69
-LibUV.v2.0.1+17.armv7l-linux-musleabihf.tar.gz/md5/f44e4b2521a813181f943895bdb0dd3c
-LibUV.v2.0.1+17.armv7l-linux-musleabihf.tar.gz/sha512/cda1413dca817f772e8b343db0c6de0ef6b8f269e9a6a2ef3403c2582aeab554f46281bbb1eb4659c259198ef47fe26aab648a281e66f80aaf2f2cda0a23ac05
-LibUV.v2.0.1+17.i686-linux-gnu.tar.gz/md5/1f231d89cf9c04515d2d107a5d786cc8
-LibUV.v2.0.1+17.i686-linux-gnu.tar.gz/sha512/089cb8a372cdee0cbc0e78fc201611bb9bafd99af9a78e09d6097a6b70e7c4aa001ebd86f944b0a885c072093c529bf86bcaa32bde4fc1934407a858c1a5a764
-LibUV.v2.0.1+17.i686-linux-musl.tar.gz/md5/01cfc2a9e2536dbd330267917abb19ce
-LibUV.v2.0.1+17.i686-linux-musl.tar.gz/sha512/72f3588cb464a60e61f8998242aaa2abdf93df920a2feba5e1d66ef0f2498488df0ec415cbb499d7f75c47bdfc7e3a2fdda6a94383492e0ad13e464eb1314ff8
-LibUV.v2.0.1+17.i686-w64-mingw32.tar.gz/md5/8ba829adad6a45dd71d5f25a7f958e59
-LibUV.v2.0.1+17.i686-w64-mingw32.tar.gz/sha512/dff3b1cfe54e583f8e9536ed02e56180b2cdb391bd108559ed97b2cafa743ebade9ddf04580912436e2efab747e09c79b99e33187ed67a27c5d38113373e1cec
-LibUV.v2.0.1+17.powerpc64le-linux-gnu.tar.gz/md5/af0e43d9d0aa91dd82b63220d96991ef
-LibUV.v2.0.1+17.powerpc64le-linux-gnu.tar.gz/sha512/9fabe3089e4fc60e910770c32d36300ce8ef36c28e8cc9c72fbecba6eb80285ee8174e84e4452fb4ce90ee7c7f94e99b03fce47d8c579bd614bfffd553f93666
-LibUV.v2.0.1+17.x86_64-apple-darwin.tar.gz/md5/871040e874eedae54553d8f1c91b9133
-LibUV.v2.0.1+17.x86_64-apple-darwin.tar.gz/sha512/d5eee08b65e4bb8b444c61ac277bec9ef944b9279dd7f0732b3cd91d47788c77938e5db71e019e01bbe7785a75df95faf14368764f700c6b7a6b9e4d96d6b4c2
-LibUV.v2.0.1+17.x86_64-linux-gnu.tar.gz/md5/d2d186952c6d017fe33f6a6bea63a3ea
-LibUV.v2.0.1+17.x86_64-linux-gnu.tar.gz/sha512/15501534bf5721e6bb668aabe6dc6375349f7a284e28df0609d00982e7e456908bd6868722391afa7f44a5c82faedc8cf544f69a0e4fb9fb0d529b3ae3d44d78
-LibUV.v2.0.1+17.x86_64-linux-musl.tar.gz/md5/271d4d40a1ae53ed5b2376e5936cfcf9
-LibUV.v2.0.1+17.x86_64-linux-musl.tar.gz/sha512/1956f059ed01f66b72349d6561b04e6a89b7257c0f838d7fbdd2cee79bd126bb46b93bf944a042b5a6a235762a7a0cdd117207342dd55a0c58653a70b4a38d48
-LibUV.v2.0.1+17.x86_64-unknown-freebsd.tar.gz/md5/62fe8523948914fbe7e28bf0b8d73594
-LibUV.v2.0.1+17.x86_64-unknown-freebsd.tar.gz/sha512/e6486888028c96975f74bc9313cba9706f6bf2be085aa776c44cbb2886753b2eee62469a0be92eb0542df1d0f51db3b34c7ba5e46842e16c6ff1d20e11b75322
-LibUV.v2.0.1+17.x86_64-w64-mingw32.tar.gz/md5/541601cf27a1d28d25b9ffb00f5aed16
-LibUV.v2.0.1+17.x86_64-w64-mingw32.tar.gz/sha512/58fd5b54694dbddc2abaccfa7291955c75818cdedbd5d9057025bc3e3e6511812e7b03f71cd839c70cd39e77c5ba3e19a07dccd579e2148a2d212fa3829a9a76
-libuv-c57e7f06cbe697ca8ea9215ce054a608c451b193.tar.gz/md5/2b81dbf80d7a9fd10806d1705dbccb7f
-libuv-c57e7f06cbe697ca8ea9215ce054a608c451b193.tar.gz/sha512/6796960a58031fa2bc9d72c8f35dff9f213e8d36bbc21ddb65f59bb4dfb074fc18414aece5a046a882dd08b42d5bd32277560c07a1298f68ab8bcd8aadcbf50b
+LibUV.v2.0.1+18.aarch64-apple-darwin.tar.gz/md5/f176c76e5e2096dea8443302cf9550b8
+LibUV.v2.0.1+18.aarch64-apple-darwin.tar.gz/sha512/4301b13953a08a758b86e30af3261fd9a291ce3829b4d98e71e2a2c040e322e284c5a6eb4bc7189cc352f4b1cf7041e2cfd3380d511d88c151df3101ad74594e
+LibUV.v2.0.1+18.aarch64-linux-gnu.tar.gz/md5/c81515783363702a1bd4b65fd6d7f36b
+LibUV.v2.0.1+18.aarch64-linux-gnu.tar.gz/sha512/011429365337f5a45e56ca7a42709866bb994c747a1170d870f5f3ddfff2d36138866ee9278ac01172bc71bde8dee404bcb9cae9c7b44222bf1cc883659df269
+LibUV.v2.0.1+18.aarch64-linux-musl.tar.gz/md5/e74d5ea4912dd326b2705638faa7b805
+LibUV.v2.0.1+18.aarch64-linux-musl.tar.gz/sha512/a26a9f2c9051816230324071c502321f7af3885d581a400615858a93a4cd457226048d15b0e7f6a73d12659763c705b5ab519e9f5b35c6d886b9fd5babbfe352
+LibUV.v2.0.1+18.armv6l-linux-gnueabihf.tar.gz/md5/6df38bcf5d0a61dee63d16b73d0c9a24
+LibUV.v2.0.1+18.armv6l-linux-gnueabihf.tar.gz/sha512/d5354a6532061de0a58965ce0e427bde52f9ae0ee39a98e1a33de4c414fddcba9ba139ddf91be7321a4ccc97bbf7a8a8357ff10cf60f83c0a6bff7d839d6d7a8
+LibUV.v2.0.1+18.armv6l-linux-musleabihf.tar.gz/md5/6f02a24cfbfae3032fadceaea1faed39
+LibUV.v2.0.1+18.armv6l-linux-musleabihf.tar.gz/sha512/7fd107eb9a5ea84b488ea02e4fbedc9fe13bb11be859986a47af38f40ad775dd9f738c790878a3503437bcac1eb26ad9fe26f4aa0d3cb45c980b4c5abc9aec99
+LibUV.v2.0.1+18.armv7l-linux-gnueabihf.tar.gz/md5/96b09dec72f7e9b7409fa2920e67c866
+LibUV.v2.0.1+18.armv7l-linux-gnueabihf.tar.gz/sha512/6a0f79fc15c944fabba5c65180b665bc9769c6ff25863e330049f48b3a4394b448492f5a9a76bb7f8dbd3ce44dfc6f9ccdc2c71c42e1c749e88070fe99b1db69
+LibUV.v2.0.1+18.armv7l-linux-musleabihf.tar.gz/md5/f44e4b2521a813181f943895bdb0dd3c
+LibUV.v2.0.1+18.armv7l-linux-musleabihf.tar.gz/sha512/cda1413dca817f772e8b343db0c6de0ef6b8f269e9a6a2ef3403c2582aeab554f46281bbb1eb4659c259198ef47fe26aab648a281e66f80aaf2f2cda0a23ac05
+LibUV.v2.0.1+18.i686-linux-gnu.tar.gz/md5/1f231d89cf9c04515d2d107a5d786cc8
+LibUV.v2.0.1+18.i686-linux-gnu.tar.gz/sha512/089cb8a372cdee0cbc0e78fc201611bb9bafd99af9a78e09d6097a6b70e7c4aa001ebd86f944b0a885c072093c529bf86bcaa32bde4fc1934407a858c1a5a764
+LibUV.v2.0.1+18.i686-linux-musl.tar.gz/md5/01cfc2a9e2536dbd330267917abb19ce
+LibUV.v2.0.1+18.i686-linux-musl.tar.gz/sha512/72f3588cb464a60e61f8998242aaa2abdf93df920a2feba5e1d66ef0f2498488df0ec415cbb499d7f75c47bdfc7e3a2fdda6a94383492e0ad13e464eb1314ff8
+LibUV.v2.0.1+18.i686-w64-mingw32.tar.gz/md5/8c6599aab9ed4c46e52f03683aac664e
+LibUV.v2.0.1+18.i686-w64-mingw32.tar.gz/sha512/13f0565f7244a8bcf1ab43fac91a856dc86d214877033a3cefee8c2179c1a275dfd7dda32e9017763acac2ba42ab6799934a58f5feaa38fb6cf2253dd713f57a
+LibUV.v2.0.1+18.powerpc64le-linux-gnu.tar.gz/md5/af0e43d9d0aa91dd82b63220d96991ef
+LibUV.v2.0.1+18.powerpc64le-linux-gnu.tar.gz/sha512/9fabe3089e4fc60e910770c32d36300ce8ef36c28e8cc9c72fbecba6eb80285ee8174e84e4452fb4ce90ee7c7f94e99b03fce47d8c579bd614bfffd553f93666
+LibUV.v2.0.1+18.x86_64-apple-darwin.tar.gz/md5/871040e874eedae54553d8f1c91b9133
+LibUV.v2.0.1+18.x86_64-apple-darwin.tar.gz/sha512/d5eee08b65e4bb8b444c61ac277bec9ef944b9279dd7f0732b3cd91d47788c77938e5db71e019e01bbe7785a75df95faf14368764f700c6b7a6b9e4d96d6b4c2
+LibUV.v2.0.1+18.x86_64-linux-gnu.tar.gz/md5/d2d186952c6d017fe33f6a6bea63a3ea
+LibUV.v2.0.1+18.x86_64-linux-gnu.tar.gz/sha512/15501534bf5721e6bb668aabe6dc6375349f7a284e28df0609d00982e7e456908bd6868722391afa7f44a5c82faedc8cf544f69a0e4fb9fb0d529b3ae3d44d78
+LibUV.v2.0.1+18.x86_64-linux-musl.tar.gz/md5/271d4d40a1ae53ed5b2376e5936cfcf9
+LibUV.v2.0.1+18.x86_64-linux-musl.tar.gz/sha512/1956f059ed01f66b72349d6561b04e6a89b7257c0f838d7fbdd2cee79bd126bb46b93bf944a042b5a6a235762a7a0cdd117207342dd55a0c58653a70b4a38d48
+LibUV.v2.0.1+18.x86_64-unknown-freebsd.tar.gz/md5/62fe8523948914fbe7e28bf0b8d73594
+LibUV.v2.0.1+18.x86_64-unknown-freebsd.tar.gz/sha512/e6486888028c96975f74bc9313cba9706f6bf2be085aa776c44cbb2886753b2eee62469a0be92eb0542df1d0f51db3b34c7ba5e46842e16c6ff1d20e11b75322
+LibUV.v2.0.1+18.x86_64-w64-mingw32.tar.gz/md5/ae103f24b6e1830cdbe02143826fe551
+LibUV.v2.0.1+18.x86_64-w64-mingw32.tar.gz/sha512/f814085c135815947f342ff24fa0e1015e283ccece84a5b8dd5ccec0f5928a129e5fd79100a33b131376ad696f70b5acadcc5a02a7e6544635ecf7e18003ba1c
+libuv-af4172ec713ee986ba1a989b9e33993a07c60c9e.tar.gz/md5/c1a7d3c74ef3999052f3bfe426264353
+libuv-af4172ec713ee986ba1a989b9e33993a07c60c9e.tar.gz/sha512/a3f16863b711ddeeb5ab8d135d7df7a4be19cc2b9821fc78c8cd3ba421231d39b7d8bd9965321455094fda01584842a58f60612d93082b4fe32210b8aa44d999
diff --git a/deps/libuv.version b/deps/libuv.version
index db6afd9f1bb51..ebfc63927d9db 100644
--- a/deps/libuv.version
+++ b/deps/libuv.version
@@ -6,4 +6,4 @@ LIBUV_JLL_NAME := LibUV
 ## source build
 LIBUV_VER := 2
 LIBUV_BRANCH=julia-uv2-1.48.0
-LIBUV_SHA1=c57e7f06cbe697ca8ea9215ce054a608c451b193
+LIBUV_SHA1=af4172ec713ee986ba1a989b9e33993a07c60c9e
diff --git a/src/sys.c b/src/sys.c
index 107a8f7637763..712d232da363a 100644
--- a/src/sys.c
+++ b/src/sys.c
@@ -478,25 +478,10 @@ JL_DLLEXPORT int jl_cpu_threads(void) JL_NOTSAFEPOINT
 
 JL_DLLEXPORT int jl_effective_threads(void) JL_NOTSAFEPOINT
 {
-    int cpu = jl_cpu_threads();
-    int masksize = uv_cpumask_size();
-    if (masksize < 0 || jl_running_under_rr(0))
-        return cpu;
-    uv_thread_t tid = uv_thread_self();
-    char *cpumask = (char *)calloc(masksize, sizeof(char));
-    int err = uv_thread_getaffinity(&tid, cpumask, masksize);
-    if (err) {
-        free(cpumask);
-        jl_safe_printf("WARNING: failed to get thread affinity (%s %d)\n", uv_err_name(err),
-                       err);
-        return cpu;
-    }
-    int n = 0;
-    for (size_t i = 0; i < masksize; i++) {
-        n += cpumask[i];
-    }
-    free(cpumask);
-    return n < cpu ? n : cpu;
+    // We want the more conservative estimate of the two.
+    int cpu_threads = jl_cpu_threads();
+    int available_parallelism = uv_available_parallelism();
+    return available_parallelism < cpu_threads ? available_parallelism : cpu_threads;
 }
 
 
diff --git a/stdlib/LibUV_jll/Project.toml b/stdlib/LibUV_jll/Project.toml
index 0c1ad8f25f848..fb03c6b996048 100644
--- a/stdlib/LibUV_jll/Project.toml
+++ b/stdlib/LibUV_jll/Project.toml
@@ -1,6 +1,6 @@
 name = "LibUV_jll"
 uuid = "183b4373-6708-53ba-ad28-60e28bb38547"
-version = "2.0.1+17"
+version = "2.0.1+18"
 
 [deps]
 Libdl = "8f399da3-3557-5675-b5ff-fb832c97cbdb"