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Replace String.split() with precompiled regex

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String.split() will allocate and compile the given regex on every call.
The networkstack process spends 2.8% of cycles doing this.

https://pprof.corp.google.com/?id=%2Fcns%2Fpf-d%2Fhome%2Fandroid-telemetry-pitot-pprof-prod-data-owner%2Fstack_sampling_pprof%2F2025-06-07%2Fstack-sampling-pprof-6187fab4-56da-4842-b9c3-9d8db45801d1.pb.gz&metric=samples&filter=hide:%255Enterp_helper%2524,focus:regex%257Csplit&pivot=com.android.networkstack.com.android.net.module.util.ProcfsParsingUtils

I randomly noticed this while looking at CPU profiles.

Flag: EXEMPT refactor
Test: ApfFilterTest and any others that may be exercising the code
Change-Id: I811c0e8982a87d10fedcda93379b08e8ab38a11b
This commit is contained in:
Shai Barack 2025-06-07 19:46:06 -07:00
commit 7c0faeeb68
1 changed files with 7 additions and 4 deletions
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11
staticlibs/device/com/android/net/module/util/ProcfsParsingUtils.java
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@ -35,6 +35,7 @@ import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Pattern;
public final class ProcfsParsingUtils {
public static final String TAG = ProcfsParsingUtils.class.getSimpleName();
@ -49,6 +50,8 @@ public final class ProcfsParsingUtils {
private static final String IPV6_MCAST_PATH = "/proc/net/igmp6";
private static final String IPV4_DEFAULT_TTL_PATH = "/proc/sys/net/ipv4/ip_default_ttl";
private static final Pattern WHITESPACE_PATTERN = Pattern.compile("\\s+");
private ProcfsParsingUtils() {
}
@ -129,7 +132,7 @@ public final class ProcfsParsingUtils {
final List<Inet6Address> addresses = new ArrayList<>();
try {
for (String line : lines) {
final String[] fields = line.split("\\s+");
final String[] fields = WHITESPACE_PATTERN.split(line);
if (!fields[1].equals(ifname)) {
continue;
}
@ -156,7 +159,7 @@ public final class ProcfsParsingUtils {
@NonNull List<String> lines, @NonNull String ifname) {
final List<MacAddress> addresses = new ArrayList<>();
for (String line: lines) {
final String[] fields = line.split("\\s+");
final String[] fields = WHITESPACE_PATTERN.split(line);
if (!fields[1].equals(ifname)) {
continue;
}
@ -182,7 +185,7 @@ public final class ProcfsParsingUtils {
final List<Inet6Address> addresses = new ArrayList<>();
try {
for (String line: lines) {
final String[] fields = line.split("\\s+");
final String[] fields = WHITESPACE_PATTERN.split(line);
if (!fields[1].equals(ifname)) {
continue;
}
@ -217,7 +220,7 @@ public final class ProcfsParsingUtils {
String name = "";
// parse output similar to `ip maddr` command (iproute2/ip/ipmaddr.c#read_igmp())
for (String line : lines) {
final String[] parts = line.trim().split("\\s+");
final String[] parts = WHITESPACE_PATTERN.split(line.trim());
if (!line.startsWith("\t")) {
name = parts[1];
if (name.endsWith(":")) {