Poul-Henning Kamp phk at phk.freebsd.dk
Thu Sep 3 10:54:19 CEST 2009

In message <4A9F5B15.8070605 at 1art.cz>, =?UTF-8?B?VsOhY2xhdiBCw61sZWs=?= writes:

>1) How does purging work with duplicate request?

We try to eliminate them, and if they are exactly identical, we succeed.

>2) is it a problem for performance to have thousands of purges?

They will cost you some memory and cpu time, but it shouldn't be a problem.

>3) how does purge request change state from "total active purges" to
>"old purges deleted" or to "duplicate purges removed"?

Old purges deleted are purges that no longer apply, ie: the have been tested
against all objects in the cache when they were entered (or the objects expired
without being requested or tested)

Duplicates are the ones above.  If you add a purge for
	req.url == "FOO"

Then any older identical purges will be marked "gone" and not tested
against, as the new purge will catch the offending objects.

(We cannot remove the old purge from the list for reference counting

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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