diff options
Diffstat (limited to 'winsup/cygwin/fhandler/pipe.cc')
| -rw-r--r-- | winsup/cygwin/fhandler/pipe.cc | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/winsup/cygwin/fhandler/pipe.cc b/winsup/cygwin/fhandler/pipe.cc index 720e4efd3..e23131668 100644 --- a/winsup/cygwin/fhandler/pipe.cc +++ b/winsup/cygwin/fhandler/pipe.cc @@ -281,6 +281,8 @@ fhandler_pipe::raw_read (void *ptr, size_t& len) size_t nbytes = 0; NTSTATUS status = STATUS_SUCCESS; IO_STATUS_BLOCK io; + ULONGLONG t0 = GetTickCount64 (); /* Init timer */ + const ULONGLONG t0_threshold = 20; if (!len) return; @@ -312,6 +314,7 @@ fhandler_pipe::raw_read (void *ptr, size_t& len) { ULONG_PTR nbytes_now = 0; ULONG len1 = (ULONG) (len - nbytes); + DWORD select_sem_timeout = 0; FILE_PIPE_LOCAL_INFORMATION fpli; status = NtQueryInformationFile (get_handle (), &io, @@ -358,7 +361,18 @@ fhandler_pipe::raw_read (void *ptr, size_t& len) nbytes = (size_t) -1; break; } - waitret = cygwait (select_sem, 1); + /* If the pipe is a non-cygwin pipe, select_sem trick + does not work. As a result, the following cygwait() + will return only after timeout occurs. This causes + performance degradation. However, setting timeout + to zero causes high CPU load. So, set timeout to + non-zero only when select_sem is valid or pipe is + not ready to read for more than t0_threshold. + This prevents both the performance degradation and + the high CPU load. */ + if (select_sem || GetTickCount64 () - t0 > t0_threshold) + select_sem_timeout = 1; + waitret = cygwait (select_sem, select_sem_timeout); if (waitret == WAIT_CANCELED) pthread::static_cancel_self (); else if (waitret == WAIT_SIGNALED) |