After running WP Super Cache on a WP3 Multisite install for a few days, I notice (looking at ismyblogworking.com graph results) that normal page response time has dropped from about 1 second to 0.5 which is excellent :)
But the feed response time has remained exactly the same as before. When I open the folder /wp-content/cache/supercache/domainname.ext/feed/ there is no index.html(.gz) and when I open the feed in an anonymous browser and look at the source footer, then refresh and look again, there is a difference in the reported generation time:
<!-- Dynamic page generated in 0.461 seconds. --> <!-- Cached page generated by WP-Super-Cache on 2011-04-08 13:53:27 --> <!-- Compression = gzip -->
I do see a corresponding file in /wp-content/cache/ with a name like
wp-cache-domainname.extxxxxxxxxx.html with matching feed content. So I suppose the feed is passed through WP-Cache instead of Super Cache... Is there a special reason for that? And why does it not improve the response time at all?
Can I make some changes in WP Super Cache settings to improve it? I tried going from PHP to mod_rewrite mode but apart from mangled gzip files (but that's another issue for which I did not try switching off server compression yet) the issue remains the same ;(