From: Fengguang Wu <fengguang.wu@intel.com>
To: Ni zhan Chen <nizhan.chen@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>,
YingHang Zhu <casualfisher@gmail.com>,
akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] mm: readahead: remove redundant ra_pages in file_ra_state
Date: Fri, 26 Oct 2012 15:09:36 +0800 [thread overview]
Message-ID: <20121026070936.GA12282@localhost> (raw)
In-Reply-To: <508A35B0.30106@gmail.com>
On Fri, Oct 26, 2012 at 03:03:12PM +0800, Ni zhan Chen wrote:
> On 10/26/2012 02:58 PM, Fengguang Wu wrote:
> >> static void shrink_readahead_size_eio(struct file *filp,
> >> struct file_ra_state *ra)
> >> {
> >>- ra->ra_pages /= 4;
> >>+ spin_lock(&filp->f_lock);
> >>+ filp->f_mode |= FMODE_RANDOM;
> >>+ spin_unlock(&filp->f_lock);
> >>
> >>As the example in comment above this function, the read maybe still
> >>sequential, and it will waste IO bandwith if modify to FMODE_RANDOM
> >>directly.
> >Yes immediately disabling readahead may hurt IO performance, the
> >original '/ 4' may perform better when there are only 1-3 IO errors
> >encountered.
>
> Hi Fengguang,
>
> Why the number should be 1-3?
The original behavior is '/= 4' on each error.
After 1 errors, readahead size will be shrinked by 1/4
After 2 errors, readahead size will be shrinked by 1/16
After 3 errors, readahead size will be shrinked by 1/64
After 4 errors, readahead size will be effectively 0 (disabled)
Thanks,
Fengguang
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WARNING: multiple messages have this Message-ID (diff)
From: Fengguang Wu <fengguang.wu@intel.com>
To: Ni zhan Chen <nizhan.chen@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>,
YingHang Zhu <casualfisher@gmail.com>,
akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] mm: readahead: remove redundant ra_pages in file_ra_state
Date: Fri, 26 Oct 2012 15:09:36 +0800 [thread overview]
Message-ID: <20121026070936.GA12282@localhost> (raw)
In-Reply-To: <508A35B0.30106@gmail.com>
On Fri, Oct 26, 2012 at 03:03:12PM +0800, Ni zhan Chen wrote:
> On 10/26/2012 02:58 PM, Fengguang Wu wrote:
> >> static void shrink_readahead_size_eio(struct file *filp,
> >> struct file_ra_state *ra)
> >> {
> >>- ra->ra_pages /= 4;
> >>+ spin_lock(&filp->f_lock);
> >>+ filp->f_mode |= FMODE_RANDOM;
> >>+ spin_unlock(&filp->f_lock);
> >>
> >>As the example in comment above this function, the read maybe still
> >>sequential, and it will waste IO bandwith if modify to FMODE_RANDOM
> >>directly.
> >Yes immediately disabling readahead may hurt IO performance, the
> >original '/ 4' may perform better when there are only 1-3 IO errors
> >encountered.
>
> Hi Fengguang,
>
> Why the number should be 1-3?
The original behavior is '/= 4' on each error.
After 1 errors, readahead size will be shrinked by 1/4
After 2 errors, readahead size will be shrinked by 1/16
After 3 errors, readahead size will be shrinked by 1/64
After 4 errors, readahead size will be effectively 0 (disabled)
Thanks,
Fengguang
next prev parent reply other threads:[~2012-10-26 7:09 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-23 12:46 [PATCH] mm: readahead: remove redundant ra_pages in file_ra_state Ying Zhu
2012-10-23 12:46 ` Ying Zhu
2012-10-23 13:21 ` Ni zhan Chen
2012-10-23 13:21 ` Ni zhan Chen
[not found] ` <CAA9v8mGMa3SDD1OLTG_wdhCGx7K-0kvSV1+MRi9uCGTz6zZaLg@mail.gmail.com>
2012-10-23 13:41 ` YingHang Zhu
2012-10-23 13:41 ` YingHang Zhu
2012-10-24 1:02 ` Ni zhan Chen
2012-10-24 1:02 ` Ni zhan Chen
2012-10-24 1:33 ` YingHang Zhu
2012-10-24 1:33 ` YingHang Zhu
2012-10-23 22:47 ` Dave Chinner
2012-10-23 22:47 ` Dave Chinner
2012-10-23 23:53 ` YingHang Zhu
2012-10-23 23:53 ` YingHang Zhu
2012-10-24 20:19 ` Dave Chinner
2012-10-24 20:19 ` Dave Chinner
2012-10-25 0:17 ` YingHang Zhu
2012-10-25 0:17 ` YingHang Zhu
2012-10-25 1:48 ` Ni zhan Chen
2012-10-25 1:48 ` Ni zhan Chen
2012-10-25 1:50 ` Dave Chinner
2012-10-25 1:50 ` Dave Chinner
2012-10-25 2:04 ` YingHang Zhu
2012-10-25 2:04 ` YingHang Zhu
2012-10-25 2:12 ` Ni zhan Chen
2012-10-25 2:12 ` Ni zhan Chen
2012-10-25 2:31 ` YingHang Zhu
2012-10-25 2:31 ` YingHang Zhu
2012-10-25 2:58 ` Fengguang Wu
2012-10-25 2:58 ` Fengguang Wu
2012-10-25 3:12 ` YingHang Zhu
2012-10-25 3:12 ` YingHang Zhu
2012-10-26 0:25 ` Dave Chinner
2012-10-26 0:25 ` Dave Chinner
2012-10-26 1:27 ` Fengguang Wu
2012-10-26 1:27 ` Fengguang Wu
2012-10-26 2:30 ` Ni zhan Chen
2012-10-26 2:30 ` Ni zhan Chen
2012-10-26 3:28 ` YingHang Zhu
2012-10-26 3:28 ` YingHang Zhu
2012-10-26 3:51 ` Ni zhan Chen
2012-10-26 3:51 ` Ni zhan Chen
2012-10-26 4:35 ` YingHang Zhu
2012-10-26 4:35 ` YingHang Zhu
2012-10-26 6:58 ` Fengguang Wu
2012-10-26 6:58 ` Fengguang Wu
2012-10-26 7:03 ` Ni zhan Chen
2012-10-26 7:03 ` Ni zhan Chen
2012-10-26 7:09 ` Fengguang Wu [this message]
2012-10-26 7:09 ` Fengguang Wu
2012-10-26 7:19 ` Ni zhan Chen
2012-10-26 7:19 ` Ni zhan Chen
2012-10-26 7:36 ` Fengguang Wu
2012-10-26 7:36 ` Fengguang Wu
2012-10-26 7:47 ` Ni zhan Chen
2012-10-26 7:47 ` Ni zhan Chen
2012-10-26 8:02 ` Fengguang Wu
2012-10-26 8:02 ` Fengguang Wu
2012-10-26 8:08 ` Ni zhan Chen
2012-10-26 8:08 ` Ni zhan Chen
2012-10-26 8:13 ` YingHang Zhu
2012-10-26 8:13 ` YingHang Zhu
2012-10-26 2:25 ` Ni zhan Chen
2012-10-26 2:25 ` Ni zhan Chen
2012-10-26 3:38 ` YingHang Zhu
2012-10-26 3:38 ` YingHang Zhu
2012-10-26 3:55 ` Fengguang Wu
2012-10-26 3:55 ` Fengguang Wu
2012-10-26 5:00 ` YingHang Zhu
2012-10-26 5:00 ` YingHang Zhu
2012-10-25 2:38 ` Fengguang Wu
2012-10-25 2:38 ` Fengguang Wu
2012-10-25 3:08 ` YingHang Zhu
2012-10-25 3:08 ` YingHang Zhu
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