Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.38 as permitted sender) client-ip=23.128.96.38;
MIME-Version: 1.0
References: <20231127220902.1315692-1-irogers@google.com> <20231127220902.1315692-5-irogers@google.com>
In-Reply-To: <20231127220902.1315692-5-irogers@google.com>
From:   Namhyung Kim <namhyung@kernel.org>
Date:   Wed, 29 Nov 2023 17:36:30 -0800
Message-ID: <CAM9d7cgMwBX2F5gVNB0OqNunbGLXniXqgcAve29P7f5C-i+BhQ@mail.gmail.com>
Subject: Re: [PATCH v5 04/50] tools api fs: Switch filename__read_str to use io.h
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>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Nick Terrell <terrelln@fb.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        Athira Rajeev <atrajeev@linux.vnet.ibm.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Vincent Whitchurch <vincent.whitchurch@axis.com>,
        "Steinar H. Gunderson" <sesse@google.com>,
        Liam Howlett <liam.howlett@oracle.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Colin Ian King <colin.i.king@gmail.com>,
        Dmitrii Dolgov <9erthalion6@gmail.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Ming Wang <wangming01@loongson.cn>,
        James Clark <james.clark@arm.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        Sean Christopherson <seanjc@google.com>,
        Leo Yan <leo.yan@linaro.org>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        German Gomez <german.gomez@arm.com>,
        Changbin Du <changbin.du@huawei.com>,
        Paolo Bonzini <pbonzini@redhat.com>, Li Dong <lidong@vivo.com>,
        Sandipan Das <sandipan.das@amd.com>,
        liuwenyu <liuwenyu7@huawei.com>, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org,
        Guilherme Amadio <amadio@gentoo.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8BIT
Precedence: bulk

On Mon, Nov 27, 2023 at 2:09 PM Ian Rogers <irogers@google.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@google.com>

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

Thanks,
Namhyung