linux-kernel - Re: [PATCH] perf record: mmap output file

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Date:	Wed, 9 Oct 2013 15:33:31 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	David Ahern <dsahern@...il.com>
Cc:	acme@...stprotocols.net, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mike Galbraith <efault@....de>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf record: mmap output file - RFC

On Sun, Sep 22, 2013 at 08:05:59PM -0600, David Ahern wrote:

SNIP

> +
> +	if (size > remaining) {
> +		memcpy(rec->mmap_addr + rec->mmap_offset, buf, remaining);
> +		rec->bytes_written += remaining;
> +
> +		size -= remaining;
> +		buf  += remaining;
> +
> +		msync(rec->mmap_addr, rec->mmap_size, MS_ASYNC);
> +		munmap(rec->mmap_addr, rec->mmap_size);

do we need msync call if munmap is called right away?


> +		goto do_mmap;

SNIP

> +	if (rec->use_mmap) {
> +		off_t len = rec->bytes_at_mmap_start + rec->bytes_written;
> +
> +		rec->use_mmap = false;
> +		msync(rec->mmap_addr, rec->mmap_size, MS_ASYNC);
> +		munmap(rec->mmap_addr, rec->mmap_size);

ditto

thanks,
jirka
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