linux-kernel - Re: [PATCH v2 2/2]: perf record: enable asynchronous trace writing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180827083457.GE24695@krava>
Date:   Mon, 27 Aug 2018 10:34:57 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 2/2]: perf record: enable asynchronous trace writing

On Thu, Aug 23, 2018 at 07:47:01PM +0300, Alexey Budankov wrote:

SNIP

> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> index e71d46cb01cc..c8b921c88a5d 100644
> --- a/tools/perf/util/mmap.c
> +++ b/tools/perf/util/mmap.c
> @@ -292,11 +292,11 @@ int perf_mmap__read_init(struct perf_mmap *map)
>  }
>  
>  int perf_mmap__push(struct perf_mmap *md, void *to,
> -		    int push(void *to, void *buf, size_t size))
> +		    int push(void *to, void *buf, size_t size, off_t), off_t *off)
>  {
>  	u64 head = perf_mmap__read_head(md);
>  	unsigned char *data = md->base + page_size;
> -	unsigned long size;
> +	unsigned long size, size0 = 0;
>  	void *buf;
>  	int rc = 0;
>  
> @@ -308,23 +308,22 @@ int perf_mmap__push(struct perf_mmap *md, void *to,
>  
>  	if ((md->start & md->mask) + size != (md->end & md->mask)) {
>  		buf = &data[md->start & md->mask];
> -		size = md->mask + 1 - (md->start & md->mask);
> -		md->start += size;
> -
> -		if (push(to, buf, size) < 0) {
> -			rc = -1;
> -			goto out;
> -		}
> +		size0 = md->mask + 1 - (md->start & md->mask);
> +		md->start += size0;
> +		memcpy(md->data, buf, size0);
>  	}
>  
>  	buf = &data[md->start & md->mask];
>  	size = md->end - md->start;
>  	md->start += size;
> +	memcpy(md->data + size0, buf, size);

this will need more comments.. and explanation why we copy the data
over to another buffer.. it's interesting, it's still faster 

jirka