On 10/09/2021 09:37, Dominik DL6ER wrote: > I agree this is a good solution, patch attached. I hope to have caught > all places (I don't have the dependencies to build all possible > combinations myself). >
Ah, thank you! I combined that with the one that started this thread and committed them. I have a tool which builds with all the possible single compile-time options, and a good selection of combinations (every possible one would take WAY to long) and it passes fine. > On Thu, 2021-09-09 at 23:35 +0100, Simon Kelley wrote: >> querystr becomes a local function to cache.c or just gets rolled into >> log_query(). > > I did the former. Merging it into log_query() would make an already > complex routine even longer. Ack. > > > Concerning performance: The loop can at most iterate over 89 entries > before it says: "Didn't find". However, for the vast vast majority of > cases, the match will be in the first 30ish (AAAA and SRV) as query > types behind those are not very likely to be seen. The loop breaks as > soon as the match is found. Looking at the gcc11 x86_64 -O2 assembly, > there are no surprises, only very few assembler instructions per > iteration are needed. The next type integers in the table can always be > found 16 bytes after the former. Hence, we just need > > .FOR_LOOP > add rax, 1 > cmp rax, 89 > je .NOT_FOUND > mov rdx, rax > movsx rcx, eax > sal rdx, 4 > cmp DWORD PTR typestr[rdx], r1d > jne .FOR_LOOP > [... stuff if found ...] > > Given we call library functions like strlen() and sprintf(), our loop > here is surely not any kind of bottleneck. Even if it'd be even larger. Agreed. It's pretty difficult to get into trouble with O(N) where N is constant and magnitude three. Cheers, Simon. tagged 2.87-test1 just to get 2.87 into the version string. Petr - I shall work though your coverity-originated patches as I get time in the next day or two. _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss
