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 4/5] Move the check for ra_pages after VM_SequentialReadHint()
Date: Wed, 26 Sep 2012 07:09:17 +0530 [thread overview]
Message-ID: <20120926013917.GB36532@Archie> (raw)
In-Reply-To: <20120922124250.GB15962@localhost>
[-- Attachment #1: Type: text/plain, Size: 2150 bytes --]
Hi,
* On Sat, Sep 22, 2012 at 08:42:50PM +0800, Fengguang Wu <fengguang.wu@intel.com> wrote:
>On Sat, Sep 22, 2012 at 04:03:13PM +0530, raghu.prabhu13@gmail.com wrote:
>> From: Raghavendra D Prabhu <rprabhu@wnohang.net>
>>
>> page_cache_sync_readahead checks for ra->ra_pages again, so moving the check
>> after VM_SequentialReadHint.
>
>Well it depends on what case you are optimizing for. I suspect there
>are much more tmpfs users than VM_SequentialReadHint users. So this
>change is actually not desirable wrt the more widely used cases.
Yes, that is true. However, it was meant to eliminate duplicate
checking of the same condition in two places. But you are right,
it may impose overhead for majority of the cases (assuming
POSIX_FADVISE is used less than tmpfs).
>
>Thanks,
>Fengguang
>
>> Signed-off-by: Raghavendra D Prabhu <rprabhu@wnohang.net>
>> ---
>> mm/filemap.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/filemap.c b/mm/filemap.c
>> index 3843445..606a648 100644
>> --- a/mm/filemap.c
>> +++ b/mm/filemap.c
>> @@ -1523,8 +1523,6 @@ static void do_sync_mmap_readahead(struct vm_area_struct *vma,
>> /* If we don't want any read-ahead, don't bother */
>> if (VM_RandomReadHint(vma))
>> return;
>> - if (!ra->ra_pages)
>> - return;
>>
>> if (VM_SequentialReadHint(vma)) {
>> page_cache_sync_readahead(mapping, ra, file, offset,
>> @@ -1532,6 +1530,9 @@ static void do_sync_mmap_readahead(struct vm_area_struct *vma,
>> return;
>> }
>>
>> + if (!ra->ra_pages)
>> + return;
>> +
>> /* Avoid banging the cache line if not needed */
>> if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
>> ra->mmap_miss++;
>> --
>> 1.7.12.1
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@kvack.org. For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
>
Regards,
--
Raghavendra Prabhu
GPG Id : 0xD72BE977
Fingerprint: B93F EBCB 8E05 7039 CD3C A4B8 A616 DCA1 D72B E977
www: wnohang.net
[-- Attachment #2: Type: application/pgp-signature, Size: 490 bytes --]
next prev parent reply other threads:[~2012-09-26 1:39 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
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 [this message]
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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