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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Mon, 24 Jul 2023 14:15:07 -0700
Message-ID: <CAKwvOd=12eSPyc5ZRgm8NPMJYjj13QOxcnHtv_Y7Ws-zffyUrA@mail.gmail.com>
Subject: Re: [PATCH v1 0/4] Perf tool LTO support
To:     Ian Rogers <irogers@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Tom Rix <trix@redhat.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        Carsten Haitzler <carsten.haitzler@arm.com>,
        Zhengjun Xing <zhengjun.xing@linux.intel.com>,
        James Clark <james.clark@arm.com>,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        bpf@vger.kernel.org, llvm@lists.linux.dev, maskray@google.com
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On Mon, Jul 24, 2023 at 1:12=E2=80=AFPM Ian Rogers <irogers@google.com> wro=
te:
>
> Add a build flag, LTO=3D1, so that perf is built with the -flto
> flag. Address some build errors this configuration throws up.

Hi Ian,
Thanks for the performance numbers. Any sense of what the build time
numbers might look like for building perf with LTO?

Does `-flto=3Dthin` in clang's case make a meaningful difference of
`-flto`? I'd recommend that over "full LTO" `-flto` when the
performance difference of the result isn't too meaningful.  ThinLTO
should be faster to build, but I don't know that I've ever built perf,
so IDK what to expect.
--=20
Thanks,
~Nick Desaulniers