Configure backing device max_ratio for FUSE filesystems.
By default FUSE filesystems have a max_ratio of 1%, meaning only 1% of
dirty pages on the system can belong to a FUSE filesystem before we
start writing back pages (and throttling, if writeback can't keep up).
This limit is useful for untrusted filesystems, but in our case, we
trust the FUSE filesystem. Since FUSE writes result in writes to the
lower filesystem, FUSE should take at most 50%. Let's start with
changing max_ratio to 40%, to avoid needless throttling.
Bug: 159254170
Bug: 159770752
Test: inspect /sys/class/bdi manually after boot
Change-Id: I467e3770fc4afba0a08fa480c0b86aa054c8b875
diff --git a/Utils.cpp b/Utils.cpp
index 6208efd..a9b7440 100644
--- a/Utils.cpp
+++ b/Utils.cpp
@@ -1386,22 +1386,54 @@
return OK;
}
+// Gets the sysfs path for parameters of the backing device info (bdi)
+static std::string getBdiPathForMount(const std::string& mount) {
+ // First figure out MAJOR:MINOR of mount. Simplest way is to stat the path.
+ struct stat info;
+ if (stat(mount.c_str(), &info) != 0) {
+ PLOG(ERROR) << "Failed to stat " << mount;
+ return "";
+ }
+ unsigned int maj = major(info.st_dev);
+ unsigned int min = minor(info.st_dev);
+
+ return StringPrintf("/sys/class/bdi/%u:%u", maj, min);
+}
+
+// Configures max_ratio for the FUSE filesystem.
+void ConfigureMaxDirtyRatioForFuse(const std::string& fuse_mount, unsigned int max_ratio) {
+ LOG(INFO) << "Configuring max_ratio of " << fuse_mount << " fuse filesystem to " << max_ratio;
+ if (max_ratio > 100) {
+ LOG(ERROR) << "Invalid max_ratio: " << max_ratio;
+ return;
+ }
+ std::string fuseBdiPath = getBdiPathForMount(fuse_mount);
+ if (fuseBdiPath == "") {
+ return;
+ }
+ std::string max_ratio_file = StringPrintf("%s/max_ratio", fuseBdiPath.c_str());
+ unique_fd fd(TEMP_FAILURE_RETRY(open(max_ratio_file.c_str(), O_WRONLY | O_CLOEXEC)));
+ if (fd.get() == -1) {
+ PLOG(ERROR) << "Failed to open " << max_ratio_file;
+ return;
+ }
+ LOG(INFO) << "Writing " << max_ratio << " to " << max_ratio_file;
+ if (!WriteStringToFd(std::to_string(max_ratio), fd)) {
+ PLOG(ERROR) << "Failed to write to " << max_ratio_file;
+ }
+}
+
// Configures read ahead property of the fuse filesystem with the mount point |fuse_mount| by
// writing |read_ahead_kb| to the /sys/class/bdi/MAJOR:MINOR/read_ahead_kb.
void ConfigureReadAheadForFuse(const std::string& fuse_mount, size_t read_ahead_kb) {
LOG(INFO) << "Configuring read_ahead of " << fuse_mount << " fuse filesystem to "
<< read_ahead_kb << "kb";
- // First figure out MAJOR:MINOR of fuse_mount. Simplest way is to stat the path.
- struct stat info;
- if (stat(fuse_mount.c_str(), &info) != 0) {
- PLOG(ERROR) << "Failed to stat " << fuse_mount;
+ std::string fuseBdiPath = getBdiPathForMount(fuse_mount);
+ if (fuseBdiPath == "") {
return;
}
- unsigned int maj = major(info.st_dev);
- unsigned int min = minor(info.st_dev);
- LOG(INFO) << fuse_mount << " has major:minor " << maj << ":" << min;
- // We found major:minor of our filesystem, time to configure read ahead!
- std::string read_ahead_file = StringPrintf("/sys/class/bdi/%u:%u/read_ahead_kb", maj, min);
+ // We found the bdi path for our filesystem, time to configure read ahead!
+ std::string read_ahead_file = StringPrintf("%s/read_ahead_kb", fuseBdiPath.c_str());
unique_fd fd(TEMP_FAILURE_RETRY(open(read_ahead_file.c_str(), O_WRONLY | O_CLOEXEC)));
if (fd.get() == -1) {
PLOG(ERROR) << "Failed to open " << read_ahead_file;