Message-ID: <553A4C18.3030609@gmail.com>
Date: Fri, 24 Apr 2015 07:58:48 -0600
From: David Ahern <dsahern@gmail.com>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.6.0
MIME-Version: 1.0
To: Yunlong Song <yunlong.song@huawei.com>, a.p.zijlstra@chello.nl,
        paulus@samba.org, mingo@redhat.com,
        Arnaldo Carvalho de Melo <acme@kernel.org>
CC: linux-kernel@vger.kernel.org, wangnan0@huawei.com
Subject: Re: [Question] How does perf still record the stack of a specified
 pid even when that process is interrupted and CPU is scheduled to other process
References: <553A45CA.8020808@huawei.com>
In-Reply-To: <553A45CA.8020808@huawei.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1167
Lines: 22

On 4/24/15 7:31 AM, Yunlong Song wrote:
> Now we are profiling the performance of ext4 and f2fs on an eMMC card with iozone,
> we find a case that ext4 is better than f2fs in random write under the test of
> "iozone -s 262144 -r 64 -i 0 -i 2". We want to analyze the I/O delay of the two
> file systems. We have got a conclusion that 1% of sys_write takes up 60% time of
> the overall sys_write (262144/64=4096). We want to find out the call stack during
> this specific 1% sys_write. Our idea is to record the stack in a certain time period
> and since the specific 1% case takes up 60% time, the total number of records of its
> stack should also takes up 60% of the total records, then we can recognize those stacks
> and figure out what the I/O stack of f2fs is doing in the 1% case.

And to address this specific profiling problem have you tried:

    perf trace record -- iozone ...
    perf trace -i perf.data -S


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/