Increase the timeout for pwrite on android

[tberghammer]

Summary

Increase the timeout for pwrite on android

The increase is necessary because with the default timeout pwrite often times out on android. Most likely it happens when a new page is created on the device.

[vharron]

Whoa. Is that 5ms? IMO, Our default timeout should be much higher than that overall.

[tberghammer]

It is measured in seconds (I don't know why) and the default timeout is 1 second.

[ovyalov]

Please see my comments.

source/Plugins/Platform/Android/PlatformAndroidRemoteGDBServer.cpp

233

It will be great to have sort of ScopedTimeout class which sets a new timeout in constructor (along with saving a previous old timeout value) and resets old value in destructor.
As I can see such pattern (set new timeout/ restore old timeout) has a few occurrences

233

For such request the transfer latency depends on a size of buffer (src_len) - is it possible to make timeout a function of buffer size?

[vharron]

It will be great to have sort of ScopedTimeout class

Yes

is it possible to make timeout a function of buffer size?

I'm nervous that adb and per-device write times are incredibly difficult to predict. We should let this be a little sloppy.

[tberghammer]

Use the ScopedTimeout class

[tberghammer]

From now on this CL is depends on D7826

source/Plugins/Platform/Android/PlatformAndroidRemoteGDBServer.cpp

233

Currently we have a previous layer which makes each request at most 1024 byte but the latency still have a huge variance (most of the request is fast, but some of them is very slow). Based on it I don't think we can make a reasonable function from buffer size to timeout because a huge part of the latency caused by factors independent from it.

233

I created the scoped timeout class (D7826) and updated this CL to use it

[tberghammer]

Abandon as D7853 make it unnecessary.

source/Plugins/Platform/Android/PlatformAndroidRemoteGDBServer.h

public:
     ~PlatformAndroidRemoteGDBServer ();
 
     lldb_private::Error
     ConnectRemote (lldb_private::Args& args) override;
 
     lldb_private::Error
     DisconnectRemote () override;
 
+    uint64_t
+    WriteFile (lldb::user_id_t fd,
+               uint64_t offset,
+               const void* data,
+               uint64_t len,
+               lldb_private::Error &error) override;
+
 protected:
     std::map<lldb::pid_t, std::pair<uint16_t, std::string>> m_port_forwards;
 
     uint16_t
     LaunchGDBserverAndGetPort (lldb::pid_t &pid) override;
 
     bool
     KillSpawnedProcess (lldb::pid_t pid) override;
 
 private:
     DISALLOW_COPY_AND_ASSIGN (PlatformAndroidRemoteGDBServer);
 
 };
 
 #endif  // liblldb_PlatformAndroidRemoteGDBServer_h_

source/Plugins/Platform/Android/PlatformAndroidRemoteGDBServer.cpp

PlatformAndroidRemoteGDBServer::DisconnectRemote ()
     if (it != m_port_forwards.end ())
     {
         DeleteForwardPortWithAdb (it->second.first, it->second.second);
         m_port_forwards.erase (it);
     }
 
     return PlatformRemoteGDBServer::DisconnectRemote ();
 }
+
+uint64_t
+PlatformAndroidRemoteGDBServer::WriteFile (lldb::user_id_t fd,
+                                           uint64_t offset,
+                                           const void* src,
+                                           uint64_t src_len,
+                                           Error &error)
+{
+    GDBRemoteCommunication::ScopedTimeout timeout (m_gdb_client, 5);
+    return PlatformRemoteGDBServer::WriteFile (fd, offset, src, src_len, error);
+}