The TTFB can also be affected if you have a large number of requests that currently queued--you can see a spike in the TTFB in periods where the server is queueing lots of requests. This could happen during periods of Garbage Collection (if you have a lot of JVM memory that needs purging) or if you just have a bunch of long running tasks (such as file uploads going on.)
-Dan >-----Original Message----- >From: Brad Wood [mailto:[EMAIL PROTECTED] >Sent: Tuesday, April 08, 2008 1:58 PM >To: CF-Talk >Subject: RE: Time to First Byte > >SeeFusion gives you two page times. The time to first byte and the >total page time. TTFB is the amount of time that elapses before CF >starts sending back data to the browser. If you are using cfflush this >could begin before the page is finished processing. Total page time is >the time that elapses before CF sends the LAST byte of information to >the browser. > >Ignoring the usage of cfflush, your TTFB is how long it took to process >your page on the CF server. The total time minus the TTFB is the time >spent transferring the response back to the client. > >Generally the latter will be very small unless you >a) are transferring a large amount of content back to the user or >b) experiencing network delays. > >Now, for your situation, I am unclear which of these figures is higher. >If the problem is simply that pages are slowing down, then you need to >figure out what they are doing. > >Use the JDBC url wrapper with SeeFusion to monitor your database calls. >Un-optimized queries should be your primary suspect. Make sure all your >data SeeFusion will tell you if a page is running a query and what SQL >is being executed. > >Now, when you see pages start slowing down, get a stack trace for the >slow request from SeeFusion and see what it is up to. > >Keep in mind that your databases performance can be impacted by DB jobs >and/or clients other than ColdFusion accessing them. > >Additionally, enable SeeFusion's db logging and check out the counters >table. That will tell you if you are having a surge of traffic, when >your average page times jumped as well as heap size etc. > >That's about as far as I can get you until you look at some stack >traces. I doubt the accessing of your .cfm files is what is slowing you >down though. They are cached locally after their first read anyway when >using trusted cache so the NAS should not even come into play after the >first load of each page. > >~Brad > >-----Original Message----- >From: Brian Peddle [mailto:[EMAIL PROTECTED] >Sent: Tuesday, April 08, 2008 12:38 PM >To: CF-Talk >Subject: Time to First Byte > >I know without deep details this may be hard to answer but looking for >some general thoughts. > >We have 4 front end web servers all on Coldfusion 7. Java 1.4.1.13. >Dell Xeon 4 gigs of Ram, dual quad core Nothing by CF runs on these >boxes. > >All the code lives on NAS on a gigabyte network. > >Throughout the day when looking at seefusion we will see short windows >of time, maybe min or 2 where pages that normally load pretty quick with > >take 30 seconds for example to execute the TTFB. Queries are in ms >range but the page just seems to stick. > >For some testing I moved all the source code to the local Drive on 1 web > >server. I do notice less pages hanging but still see little blips. >What I see as a big difference is when my app first loads on the NAS it >takes up to 100 seconds, locally 10 seconds or less to load in all the >objects. Performance overall on the local machine seems faster. Roght >now the code on the local machine sits on C drive as well so I suspect >if I added some more drives it would perform a little better with having > >to compete with the OS. > >For caching I have both Trusted cache and Save Class files checked and >max number of cached templates at 2000. Max is connections is at 24, I >know I could go much higher but this seems to work best. > >I would assume overall that the site running locally will perform faster > >than over a gig switch. Maybe fiber would compete here, not sure. > >Im trying to figure out why the sporadic high TTFB comes up. Are there >any other settings, places to look, IIS settings maybe, to try and see >why this is happening... or is it simply a burst in traffic that causes >some concurrency issues? > >Thanks in advance. > >Brian > > > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Adobe® ColdFusion® 8 software 8 is the most important and dramatic release to date Get the Free Trial http://ad.doubleclick.net/clk;192386516;25150098;k Archive: http://www.houseoffusion.com/groups/CF-Talk/message.cfm/messageid:302975 Subscription: http://www.houseoffusion.com/groups/CF-Talk/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.4
