From: Raghavendra D Prabhu <raghu.prabhu13@gmail.com>
To: Fengguang Wu <fengguang.wu@intel.com>
Cc: linux-mm@kvack.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org
Subject: Re: Re: [PATCH 2/5] mm/readahead: Change the condition for SetPageReadahead
Date: Wed, 26 Sep 2012 06:59:00 +0530 [thread overview]
Message-ID: <20120926012900.GA36532@Archie> (raw)
In-Reply-To: <20120922124920.GB17562@localhost>
[-- Attachment #1: Type: text/plain, Size: 1797 bytes --]
Hi,
* On Sat, Sep 22, 2012 at 08:49:20PM +0800, Fengguang Wu <fengguang.wu@intel.com> wrote:
>On Sat, Sep 22, 2012 at 04:03:11PM +0530, raghu.prabhu13@gmail.com wrote:
>> From: Raghavendra D Prabhu <rprabhu@wnohang.net>
>>
>> If page lookup from radix_tree_lookup is successful and its index page_idx ==
>> nr_to_read - lookahead_size, then SetPageReadahead never gets called, so this
>> fixes that.
>
>NAK. Sorry. It's actually an intentional behavior, so that for the
>common cases of many cached files that are accessed frequently, no
>PG_readahead will be set at all to pointlessly trap into the readahead
>routines once and again.
ACK, thanks for explaining that. However, regarding this, I would
like to know if the implications of the patch
51daa88ebd8e0d437289f589af29d4b39379ea76 will still apply if
PG_readahead is not set.
>
>Perhaps we need a patch for commenting that case. :)
>
>Thanks,
>Fengguang
>
>> Signed-off-by: Raghavendra D Prabhu <rprabhu@wnohang.net>
>> ---
>> mm/readahead.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/readahead.c b/mm/readahead.c
>> index 461fcc0..fec726c 100644
>> --- a/mm/readahead.c
>> +++ b/mm/readahead.c
>> @@ -189,8 +189,10 @@ __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
>> break;
>> page->index = page_offset;
>> list_add(&page->lru, &page_pool);
>> - if (page_idx == nr_to_read - lookahead_size)
>> + if (page_idx >= nr_to_read - lookahead_size) {
>> SetPageReadahead(page);
>> + lookahead_size = 0;
>> + }
>> ret++;
>> }
>>
>> --
>> 1.7.12.1
>
Regards,
--
Raghavendra Prabhu
GPG Id : 0xD72BE977
Fingerprint: B93F EBCB 8E05 7039 CD3C A4B8 A616 DCA1 D72B E977
www: wnohang.net
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next prev parent reply other threads:[~2012-09-26 1:29 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-22 10:33 [PATCH 0/5] Readahead fixes / improvements raghu.prabhu13
[not found] ` <cover.1348309711.git.rprabhu@wnohang.net>
2012-09-22 10:33 ` [PATCH 1/5] mm/readahead: Check return value of read_pages raghu.prabhu13
2012-09-22 12:43 ` Fengguang Wu
2012-09-26 1:25 ` Raghavendra D Prabhu
2012-09-28 11:54 ` Fengguang Wu
2012-10-16 17:47 ` Raghavendra D Prabhu
2012-10-17 2:53 ` Fengguang Wu
2012-09-22 10:33 ` [PATCH 2/5] mm/readahead: Change the condition for SetPageReadahead raghu.prabhu13
2012-09-22 12:49 ` Fengguang Wu
2012-09-26 1:29 ` Raghavendra D Prabhu [this message]
2012-09-28 11:56 ` Fengguang Wu
2012-10-16 17:42 ` Raghavendra D Prabhu
2012-10-17 2:34 ` Fengguang Wu
2012-09-22 10:33 ` [PATCH 3/5] Remove file_ra_state from arguments of count_history_pages raghu.prabhu13
2012-09-22 12:40 ` Fengguang Wu
2012-10-16 18:21 ` Raghavendra D Prabhu
2012-10-17 3:15 ` Fengguang Wu
2012-09-22 10:33 ` [PATCH 4/5] Move the check for ra_pages after VM_SequentialReadHint() raghu.prabhu13
2012-09-22 12:42 ` Fengguang Wu
2012-09-26 1:39 ` Raghavendra D Prabhu
2012-10-16 18:15 ` Raghavendra D Prabhu
2012-10-17 3:13 ` Fengguang Wu
2012-09-22 10:33 ` [PATCH 5/5] mm/readahead: Use find_get_pages instead of radix_tree_lookup raghu.prabhu13
2012-09-22 13:15 ` Fengguang Wu
2012-09-26 2:58 ` Raghavendra D Prabhu
2012-09-28 12:18 ` Fengguang Wu
2012-10-16 16:59 ` Raghavendra D Prabhu
2012-10-17 2:12 ` Fengguang Wu
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