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Date: Tue, 12 Jan 2016 17:28:28 +0800
From: "Wangnan (F)" <wangnan0@huawei.com>
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To: Jiri Olsa <jolsa@kernel.org>, Arnaldo Carvalho de Melo <acme@kernel.org>
CC: lkml <linux-kernel@vger.kernel.org>, David Ahern <dsahern@gmail.com>,
        "Ingo Molnar" <mingo@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [RFC 6/6] perf build: Introduce FEATURES_DUMP make variable
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On 2016/1/11 18:54, Jiri Olsa wrote:
> Introducing FEATURES_DUMP make variable to provide features
> detection dump file and bypass the feature detection.
>
> The intention is to use this during build tests to skip
> repeated features detection, like:
>
> Get feature dump static build into /tmp/fd file:
>    $ make feature-dump FEATURE_DUMP_COPY=/tmp/fd LDFLAGS=-static
>      BUILD:   Doing 'make -j4' parallel build
>
>    Auto-detecting system features:
>    ...                         dwarf: [ OFF ]
>
>    SNIP
>
>    FEATURE-DUMP file copied into /tmp/fd
>
> Use /tmp/fd to build perf:
>    $ make FEATURES_DUMP=/tmp/fd LDFLAGS=-static
>
>    $ file perf
>    perf: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, for ...
>
> Suggested-by: Wang Nan <wangnan0@huawei.com>
> Link: http://lkml.kernel.org/n/tip-fhb47m6t18txuwrzu33is2bo@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---

Thank you for these two patch. However I found a small limitation.
I must skip 'make clean' between two feature-dump, or the result is wrong.

For example:

$ make feature-dump LDFLAGS="-static"
   BUILD:   Doing 'make -j24' parallel build

Auto-detecting system features:
<SNIP>
...                          zlib: [ on  ]
...                          lzma: [ OFF ]     <--- looks good. I don't 
have static lzma library
...                     get_cpuid: [ on  ]
...                           bpf: [ on  ]


$ make feature-dump
   BUILD:   Doing 'make -j24' parallel build

Auto-detecting system features:
<SNIP>
...                          zlib: [ on  ]
...                          lzma: [ on  ]   <--- also good
...                     get_cpuid: [ on  ]
...                           bpf: [ on  ]


$ make feature-dump LDFLAGS="-static"
   BUILD:   Doing 'make -j24' parallel build

Auto-detecting system features:
<SNIP>
...                          zlib: [ on  ]
...                          lzma: [ on  ]     <--- Bad...
...                     get_cpuid: [ on  ]
...                           bpf: [ on  ]

Thank you.