logd: Add minimum time bucket statistics
* Only enabled for dev builds because halves performance.
- Used to establish if /proc/sys/net/unix/max_dgram_qlen
is appropriate for the platform
(see logd/LogStatistics.cpp comments)
- enabled if logd.dgram_qlen.statistics is not zero/empty
Change-Id: Ib8ecfeb75b6f0f954c099a6b1032b8afb5efcbd4
diff --git a/logd/LogStatistics.cpp b/logd/LogStatistics.cpp
index 49ee50d..5622ee5 100644
--- a/logd/LogStatistics.cpp
+++ b/logd/LogStatistics.cpp
@@ -275,6 +275,66 @@
mSizes[i] = 0;
mElements[i] = 0;
}
+
+ dgram_qlen_statistics = false;
+ for(unsigned short bucket = 0; dgram_qlen(bucket); ++bucket) {
+ mMinimum[bucket].tv_sec = (uint32_t)-1;
+ mMinimum[bucket].tv_nsec = 999999999UL;
+ }
+}
+
+// Each bucket below represents a dgram_qlen of log messages. By
+// finding the minimum period of time from start to finish
+// of each dgram_qlen, we can get a performance expectation for
+// the user space logger. The net result is that the period
+// of time divided by the dgram_qlen will give us the average time
+// between log messages; at the point where the average time
+// is greater than the throughput capability of the logger
+// we will not longer require the benefits of the FIFO formed
+// by max_dgram_qlen. We will also expect to see a very visible
+// knee in the average time between log messages at this point,
+// so we do not necessarily have to compare the rate against the
+// measured performance (BM_log_maximum_retry) of the logger.
+//
+// for example (reformatted):
+//
+// Minimum time between log events per dgram_qlen:
+// 1 2 3 5 10 20 30 50 100 200 300 400 500 600
+// 5u2 12u 13u 15u 16u 27u 30u 36u 407u 3m1 3m3 3m9 3m9 5m5
+//
+// demonstrates a clear knee rising at 100, so this means that for this
+// case max_dgram_qlen = 100 would be more than sufficient to handle the
+// worst that the system could stuff into the logger. The
+// BM_log_maximum_retry performance (derated by the log collection) on the
+// same system was 33.2us so we would almost be fine with max_dgram_qlen = 50.
+// BM_log_maxumum_retry with statistics off is roughly 20us, so
+// max_dgram_qlen = 20 would work. We will be more than willing to have
+// a large engineering margin so the rule of thumb that lead us to 100 is
+// fine.
+//
+// bucket dgram_qlen are tuned for /proc/sys/net/unix/max_dgram_qlen = 300
+const unsigned short LogStatistics::mBuckets[] = {
+ 1, 2, 3, 5, 10, 20, 30, 50, 100, 200, 300, 400, 500, 600
+};
+
+unsigned short LogStatistics::dgram_qlen(unsigned short bucket) {
+ if (bucket >= sizeof(mBuckets) / sizeof(mBuckets[0])) {
+ return 0;
+ }
+ return mBuckets[bucket];
+}
+
+unsigned long long LogStatistics::minimum(unsigned short bucket) {
+ if (mMinimum[bucket].tv_sec == LONG_MAX) {
+ return 0;
+ }
+ return mMinimum[bucket].nsec();
+}
+
+void LogStatistics::recordDiff(log_time diff, unsigned short bucket) {
+ if ((diff.tv_sec || diff.tv_nsec) && (mMinimum[bucket] > diff)) {
+ mMinimum[bucket] = diff;
+ }
}
void LogStatistics::add(unsigned short size,
@@ -352,6 +412,9 @@
log_id_for_each(i) {
if (logMask & (1 << i)) {
oldLength = string.length();
+ if (spaces < 0) {
+ spaces = 0;
+ }
string.appendFormat("%*s%s", spaces, "", android_log_id_to_name(i));
spaces += spaces_total + oldLength - string.length();
}
@@ -369,6 +432,9 @@
continue;
}
oldLength = string.length();
+ if (spaces < 0) {
+ spaces = 0;
+ }
string.appendFormat("%*s%zu/%zu", spaces, "",
sizesTotal(i), elementsTotal(i));
spaces += spaces_total + oldLength - string.length();
@@ -388,12 +454,64 @@
size_t els = elements(i);
if (els) {
oldLength = string.length();
+ if (spaces < 0) {
+ spaces = 0;
+ }
string.appendFormat("%*s%zu/%zu", spaces, "", sizes(i), els);
spaces -= string.length() - oldLength;
}
spaces += spaces_total;
}
+ if (dgram_qlen_statistics) {
+ const unsigned short spaces_time = 6;
+ const unsigned long long max_seconds = 100000;
+ spaces = 0;
+ string.append("\n\nMinimum time between log events per dgram_qlen:\n");
+ for(unsigned short i = 0; dgram_qlen(i); ++i) {
+ oldLength = string.length();
+ if (spaces < 0) {
+ spaces = 0;
+ }
+ string.appendFormat("%*s%u", spaces, "", dgram_qlen(i));
+ spaces += spaces_time + oldLength - string.length();
+ }
+ string.append("\n");
+ spaces = 0;
+ unsigned short n;
+ for(unsigned short i = 0; (n = dgram_qlen(i)); ++i) {
+ unsigned long long duration = minimum(i);
+ if (duration) {
+ duration /= n;
+ if (duration >= (NS_PER_SEC * max_seconds)) {
+ duration = NS_PER_SEC * (max_seconds - 1);
+ }
+ oldLength = string.length();
+ if (spaces < 0) {
+ spaces = 0;
+ }
+ string.appendFormat("%*s", spaces, "");
+ if (duration >= (NS_PER_SEC * 10)) {
+ string.appendFormat("%llu",
+ (duration + (NS_PER_SEC / 2))
+ / NS_PER_SEC);
+ } else if (duration >= (NS_PER_SEC / (1000 / 10))) {
+ string.appendFormat("%llum",
+ (duration + (NS_PER_SEC / 2 / 1000))
+ / (NS_PER_SEC / 1000));
+ } else if (duration >= (NS_PER_SEC / (1000000 / 10))) {
+ string.appendFormat("%lluu",
+ (duration + (NS_PER_SEC / 2 / 1000000))
+ / (NS_PER_SEC / 1000000));
+ } else {
+ string.appendFormat("%llun", duration);
+ }
+ spaces -= string.length() - oldLength;
+ }
+ spaces += spaces_time;
+ }
+ }
+
log_id_for_each(i) {
if (!(logMask & (1 << i))) {
continue;
@@ -433,7 +551,7 @@
if (!oneline) {
first = true;
- } else if (!first && spaces) {
+ } else if (!first && (spaces > 0)) {
string.appendFormat("%*s", spaces, "");
}
spaces = 0;
@@ -458,10 +576,16 @@
size_t els = up->elements();
if (els == elsTotal) {
+ if (spaces < 0) {
+ spaces = 0;
+ }
string.appendFormat("%*s=", spaces, "");
spaces = -1;
} else if (els) {
oldLength = string.length();
+ if (spaces < 0) {
+ spaces = 0;
+ }
string.appendFormat("%*s%zu/%zu", spaces, "", up->sizes(), els);
spaces -= string.length() - oldLength;
}
@@ -502,7 +626,7 @@
continue;
}
- if (!first && spaces) {
+ if (!first && (spaces > 0)) {
string.appendFormat("%*s", spaces, "");
}
spaces = 0;
@@ -517,10 +641,16 @@
spaces += spaces_total + oldLength - string.length();
if (els == elsTotal) {
+ if (spaces < 0) {
+ spaces = 0;
+ }
string.appendFormat("%*s=", spaces, "");
spaces = -1;
} else if (els) {
oldLength = string.length();
+ if (spaces < 0) {
+ spaces = 0;
+ }
string.appendFormat("%*s%zu/%zu", spaces, "",
pp->sizes(), els);
spaces -= string.length() - oldLength;
@@ -531,7 +661,7 @@
}
if (gone_els) {
- if (!first && spaces) {
+ if (!first && (spaces > 0)) {
string.appendFormat("%*s", spaces, "");
}