linux-kernel - Re: [PATCH v5 04/50] tools api fs: Switch filename__read

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Message-ID: <CAM9d7cgMwBX2F5gVNB0OqNunbGLXniXqgcAve29P7f5C-i+BhQ@mail.gmail.com>
Date:   Wed, 29 Nov 2023 17:36:30 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Nick Terrell <terrelln@...com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        "Steinar H. Gunderson" <sesse@...gle.com>,
        Liam Howlett <liam.howlett@...cle.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Colin Ian King <colin.i.king@...il.com>,
        Dmitrii Dolgov <9erthalion6@...il.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Ming Wang <wangming01@...ngson.cn>,
        James Clark <james.clark@....com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Leo Yan <leo.yan@...aro.org>,
        Ravi Bangoria <ravi.bangoria@....com>,
        German Gomez <german.gomez@....com>,
        Changbin Du <changbin.du@...wei.com>,
        Paolo Bonzini <pbonzini@...hat.com>, Li Dong <lidong@...o.com>,
        Sandipan Das <sandipan.das@....com>,
        liuwenyu <liuwenyu7@...wei.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Guilherme Amadio <amadio@...too.org>
Subject: Re: [PATCH v5 04/50] tools api fs: Switch filename__read_str to use io.h

On Mon, Nov 27, 2023 at 2:09 PM Ian Rogers <irogers@...gle.com> wrote:
>
> filename__read_str has its own string reading code that allocates
> memory before reading into it. The memory allocated is sized at BUFSIZ
> that is 8kb. Most strings are short and so most of this 8kb is
> wasted.
>
> Refactor io__getline, as io__getdelim, so that the newline character
> can be configurable and ignored in the case of filename__read_str.
>
> Code like build_caches_for_cpu in perf's header.c will read many
> strings and hold them in a data structure, in this case multiple
> strings per cache level per CPU. Using io.h's io__getline avoids the
> wasted memory as strings are temporarily read into a buffer on the
> stack before being copied to a buffer that grows 128 bytes at a time
> and is never sized larger than the string.
>
> For a 16 hyperthread system the memory consumption of "perf record
> true" is reduced by 180kb, primarily through saving memory when
> reading the cache information.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung