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Date: Fri, 8 Apr 2022 22:59:55 +0200
From: Mark Wielaard <mark@klomp.org>
To: Milian Wolff <mail@milianw.de>
Cc: "Frank Ch. Eigler" <fche@redhat.com>, elfutils-devel@sourceware.org
Subject: Re: caching failed lookups of debuginfo?
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Hi Milian,

On Fri, Apr 08, 2022 at 10:45:10PM +0200, Milian Wolff wrote:
> In the off-CPU flame graphs I clearly see this callchain when DEBUGINFOD_URLS 
> is set:
> 
> ```
> dwfl_standard_find_debuginfo > debuginfod_query_server > curl_multi_wait
> ```
> 
> This accounts for ~2.5s of off-CPU time in my case. If you are saying that 
> negative lookups are cached, then what is this? Why would a second run of the 
> same dwfl-using application with the same input data keep querying the server?

That is certainly not what should happen once the cache is filled.
Could you run with DEBUGINFOD_VERBOSE=1 to see what is being fetched and why?

Thanks,

Mark