Hi Yann, Thanks for your explanation. I got the issue. Actually NonStop has maximum limit of 52KB only for writev. Therefore I was getting 4022 after 49KB. Because after 49KB, apache is adding 8K more bytes which leads to 56KB. Therefore, writev was failing.
To solve this, I have changed THRESHOLD_MAX_BUFFER in core_filter.c to 50000. But again I am seeing that after 49KB, apache is adding 8192 Bytes in it, which leads to failure of writev again. Do I need to change in more places or the above fix should work. Thanks Hemant On Sun, Sep 16, 2018 at 4:48 PM Yann Ylavic <ylavic....@gmail.com> wrote: > Hi Hermant, > > On Fri, Sep 14, 2018 at 1:53 PM Hemant Chaudhary > <hemantdude.chaudh...@gmail.com> wrote: > > > > Please don't get confuse with Cygwin(Windows). I am running apache on > NonStop(Tandem). > > Well, isn't the error_log attached to the previous message relevant > (be it cygwin or not)? > Btw, LogLevel trace6 would help here. > > > I have put breakpoint at apr_poll() but it is not going there. > > > > Few Events of writing : > > 1) apache writes 779 bytes to tomcat from apr_socket_sendv() function > and writev functions returns success. > > 2) apache writes 24604 bytes to tomcat from apr_socket_sendv() function > but writev function returns -1 with EWOULDBLOCK and it has > timeout=0(because set in writev_nonblocking()) > > 3) apache again tries to write 32796 to tomcat from apr_socket_sendv() > function but writev function returns -1 with EWOULDBLOCK and it has > timeout=0(because set in writev_nonblocking()). > > 4) apache again tries to write 40988 to tomcat from apr_socket_sendv() > function but writev function returns -1 with EWOULDBLOCK and it has > timeout=0(because set in writev_nonblocking()). > > 5) apache again tries to write 49180 to tomcat from apr_socket_sendv() > function but writev function returns -1 with EWOULDBLOCK and it has > timeout=0(because set in writev_nonblocking()). > > OK, all those EWOULDBLOCK make the core output filter to bufferize the > "pending" data for the next time it's called. > > > 6) After this I am getting 4022 error. > > Here the 64K bufferized limit/threshold is reached > (non_file_bytes_in_brigade >= THRESHOLD_MAX_BUFFER in > ap_core_output_filter()), so the core output filter can't continue > nonblocking anymore and enters send_brigade_blocking(), which does > send_brigade_nonblocking() + apr_poll() until the 64K buffer is sent > completely. > > However it seems that on your system the first call to > send_brigade_nonblocking() fails (since apr_poll() is never called), > possibly a limit on apr_socket_sendv() (i.e. writev() syscall), either > more than 64K total bytes or nvec > 4? > > I think you need to debug/gdb in send_brigade_nonblocking() for this > last call and determine where and why send_brigade_nonblocking() => > writev_nonblocking() => apr_socket_send() => writev(vec, nvec) fails. > Maybe a unit test (a simple standalone main() program) can determine > the limits for writev() on your system, so that the right values for > THRESHOLD_MAX_BUFFER and MAX_IOVEC_TO_WRITE (in > "server/core_filters.c") can be tuned for NonStop(Tandem) ... > > Hope that helps, > Yann. > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@httpd.apache.org > For additional commands, e-mail: users-h...@httpd.apache.org > >
