HUP frees a load of configuration and the re-reads it and I correlated all the memory freed by the second HUP with what was allocated in the first HUP.
It's perfect. Every block is freed.This is a fairly old installation, so old libraries, etc, but the very latest dnsmasq code.
The configuration it's re-reading is pretty small. I then tried your technique of hitting dnsmasq hard with many HUPs.I had to go up to half a million to see much effect, but I guess most of those were dropped since they will have arrived before the previous one was cleared.
In any case I could see a reproducible rise of a few percent in the VSZ of the process each time.
What's clear is that the configuration is stored in a _lot_ of small allocations, so re-reading a substantial configuration will free a lot of small blocks and then malloc a lot of small blocks.
A quick Google produces some complaints about the fragmentation performance of musl, which may be significant.
Is your installation using musl as the C library, and is it possible to build dnsmasq against, say glibc to test?
Nearly all of the memory management on dnsmasq that gets hit by answering DNS or DHCP requests avoid hammering the malloc system by building pools of free data structures that get re-cycled as needed. Once the pools have grown to equilibrium size, even a very busy server hardly uses the heap. I guess the configuration code to use the same policy, but it's a big re-write, and re-reading configuration on a sub-second timescale is an unlikely use-case.
Cheers, Simon. On 30.01.2026 01:59, Y.Y. wrote:
*Hi Simon,*I think Your suspicion about the configuration re-reading logic is spot on. I have documented the reproduction and some analysis here: https:// github.com/openwrt/openwrt/issues/21729#issuecomment-3815442601 <https://github.com/openwrt/openwrt/issues/21729#issuecomment-3815442601>To assist with the debugging, I can provide an OpenWrt *Linux x86_64 VM image* that consistently reproduces this memory leak. Please let me know if this would be helpful for your investigation._______________________________________________ Dnsmasq-discuss mailing list [email protected] https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss
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