liblog: logd: Add android_lookupEventTag_len()
Allows us to mitigate the impact of MAP_PRIVATE and copy on write by
calling android_lookupEventTag_len instead of android_lookupEventTag,
and delaying the copy on write impact to the later. We return a
string length in a supplied location along with the string pointer
with android_lookupEventTag_len(const EventTagMap* map, size_t* len,
int tag). The string is not guaranteed to be nul terminated. Since
android_lookupEventTag() called even once can cause the memory
impact, we will mark it as deprecated, but we currently have no
timeframe for removal since this is a very old interface.
Add an API for __android_log_is_loggable_len() that accepts the non
null terminated content and fixup callers that would gain because the
length is known prior to the call either in the compiler or at
runtime. Tackle transition to android_lookupEventTag_len() and
fixup callers.
On any application that performs logging (eg: com.android.phone)
/proc/<pid>/smaps before:
xxxxxxxxxx-xxxxxxxxxx rw-p 00000000 fd:00 463 /system/etc/event-log-tags
Size: 20 kB
Rss: 20 kB
Pss: 1 kB
Shared_Clean: 0 kB
Shared_Dirty: 20 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 0 kB
Anonymous: 20 kB
AnonHugePages: 0 kB
Swap: 0 kB
SwapPss: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Locked: 0 kB
VmFlags: rd wr mr mw me ac
/proc/<pid>/smaps after:
xxxxxxxxxx-xxxxxxxxxx rw-p 00000000 fd:00 1773 /system/etc/event-log-tags
Size: 20 kB
Rss: 20 kB
Pss: 1 kB
Shared_Clean: 20 kB (was 0kB)
Shared_Dirty: 0 kB (was 20kB)
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 20 kB (was 0kB)
Anonymous: 0 kB (was 20kB)
AnonHugePages: 0 kB
Swap: 0 kB
SwapPss: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Locked: 0 kB
VmFlags: rd wr mr mw me ac
Added liblog-unit-tests --gtest_filter=liblog.event_log_tags to
check for Shared_Clean: to not be 0 and Anonymous: to be 0 for
all processes referencing event-log-tags. Which can include multiple
references to /system/etc/event-log-tags and future possible refs to
/data/misc/logd/event-log-tags and /dev/event-log-tags. We want
failure messages to help point to errant code using the deprecated
interface.
This change saves 1/4MB of memory or more on a typical system.
Test: gTest liblog-unit-tests
Bug: 31456426
Change-Id: I9e08e44d9092bd96fe704b5709242e7195281d33
18 files changed