Have a machine running the latest devel version nginx-0.7.33 (tried 0.6.35 with same results) for serving small (less than 10K images) and am seeing on tcpdump that some SYN packets are not responded to right away.<div>The browser does retransmit these image requests every second and on the 2nd or 3rd resent SYN, I finally start seeing and ACK, and the images load.</div>
<div>It is very indeterministic as to when it happens and can only reproduce it some of the time. When it does occur the outcome is a page with some images loaded and others (whose SYN packets are not ACKs) are not loaded.....a few seconds later they load.</div>
<div>Typically the system has ~2000 active connections, most in keep alive. The load is around 100-200 req/sec.</div><div><br></div><div>I have tries all sorts of settings and configurations suggested in the maillist but I still dont have the solution for this issue. from 1 to 4 workers, changing the connection counts, different even handlers, kernel buffers, etc.<br>
</div><div>It just seems so anecdotal to just change a bunch of settings without being able to what is happening internally.<br></div><div>I'd like to be able to debug a little deeper to find out what is happening to these packets.<br>
</div><div><br></div><div><div>How would I go about debugging what is the cause of it. Is it the interface driver, kernel, or nginx? What kind of tools and debugging options can I try next?</div><div><br></div><div>Thanks, Radek</div>
</div><div><br></div><div><br></div><div>System Details<br></div><div>model name : Intel(R) Xeon(R) CPU X3210 @ 2.13GHz<br></div><div><div>Linux n06 2.6.18-92.1.22.el5 #1 SMP Tue Dec 16 12:03:43 EST 2008 i686 i686 i386 GNU/Linux</div>
<div>eth0</div><div>Advertised auto-negotiation: Yes</div><div>Speed: 1000Mb/s</div><div>Duplex: Full</div><div>Port: Twisted Pair</div><div>PHYAD: 1</div><div>Transceiver: internal</div><div>Auto-negotiation: on</div><div>
Supports Wake-on: g</div><div>Wake-on: d</div><div>Current message level: 0x000000ff (255)</div><div>Link detected: yes</div><div>driver: tg3</div><div>version: 3.86</div><div>firmware-version: 5721-v3.61, ASFIPMI v6.21</div>
<div>bus-info: 0000:05:00.0</div><div><br></div><div>avg-cpu: %user %nice %system %iowait %steal %idle</div><div>0.10 0.00 0.20 2.43 0.00 97.27</div><div>Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util</div>
<div>sda 0.00 0.00 27.40 0.00 443.20 0.00 16.18 0.10 3.50 3.32 9.10</div><div>no overruns or errors on interface.</div></div>