Bug #46723 [Fbk->Asn]: FastCGI is incredibly slow due to TCP ack delay

Edit report at http://bugs.php.net/bug.php?id=46723&edit=1 ID: 46723 User updated by: jost_boekemeier at users dot sf dot net Reported by: jost_boekemeier at users dot sf dot net Summary: FastCGI is incredibly slow due to TCP ack delay -Status: Feedback +Status: Assigned Type: Bug Package: CGI related Operating System: * PHP Version: 5CVS, 6CVS (2008-12-08) Assigned To: dmitry Block user comment: N New Comment: Test machine was FC10 with a fedora-patched kernel 2.6.25. It is possible to eliminate the ack delay on kernel-level (e.g. make NDELAY default for local tcp connections). But in fc9, fc10 and fc11 the problem was, and in FreeBSD the problem is, very visible. Bridge0 was identical to Bridge except for the NDELAY patch. An alternative approach would be to add a write cache which grows dynamically, and which is flushed each time read() is called. But I think this is too much overhead. Previous Comments: ------------------------------------------------------------------------ [2010-08-25 14:55:39] dmitry@php.net I've tested your patch on Linux 2.6.27 and it doesn't make any visible difference. May be you used different URLs? (In your last post JavaBridge != JavaBridgeO) Also it would be better to use special programs to benchmark (e.g. ab or http_load) ------------------------------------------------------------------------ [2010-03-20 18:41:35] jost_boekemeier at users dot sf dot net Please excuse the delay. I didn't noticed that you were asking for a patch. After applying the patch fastcgi renders 900 pages in 1m8.095s, compared to 1m40.428s before. [notice for me] $ time for i in seq 900; do wget -O/dev/null -o/dev/null http://localhost:8080/JavaBridge/sessionSharing.php; done real 1m40.428s user 0m1.587s sys 0m3.108s $ time for i in seq 900; do wget -O/dev/null -o/dev/null http://localhost:8080/JavaBridgeO/sessionSharing.php; done real 1m8.095s user 0m1.212s sys 0m2.485s ------------------------------------------------------------------------ [2009-01-29 01:00:16] php-bugs at lists dot php dot net No feedback was provided for this bug for over a week, so it is being suspended automatically. If you are able to provide the information that was originally requested, please do so and change the status of the bug back to "Open". ------------------------------------------------------------------------ [2009-01-21 19:27:40] jani@php.net Patches are always welcome, you don't need to wait for a request..:) ------------------------------------------------------------------------ [2008-11-30 17:42:32] jost_boekemeier at users dot sf dot net Description: ------------ The PHP side of a socket-based FastCGI communication is unbuffered since PHP 5.1.4 (maybe earlier). write/write/read cycles have a huge performance impact, on the latest Linux kernel the FastCGI SAPI is actually slower than executing a CGI for each request! The actual problem is caused by the two unbuffered write() operations, which run into a delayed ack and therefore cause a latency of 40000us on FC10 and 500ms(!) on FreeBSD. As an immediate fix I suggest to switch on NDELAY for the PHP FastCGI socket communication. I can provide a patch if you want me to. Regards, Jost Bökemeier Reproduce code: --------------- - Expected result: ---------------- - Actual result: -------------- - ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/bug.php?id=46723&edit=1