Re: [PATCH] readahead:add blk_run_backing_dev

Hisashi Hifumi
2009-05-20T01:47:06Z

At 10:07 09/05/20, KOSAKI Motohiro wrote:
>(cc to Wu and linux-mm)
>
>> Hi.
>>
>> I wrote a patch that adds blk_run_backing_dev on page_cache_async_readahead
>> so readahead I/O is unpluged to improve throughput.
>>
>> Following is the test result with dd.
>>
>> #dd if=testdir/testfile of=/dev/null bs=16384
>>
>> -2.6.30-rc6
>> 1048576+0 records in
>> 1048576+0 records out
>> 17179869184 bytes (17 GB) copied, 224.182 seconds, 76.6 MB/s
>>
>> -2.6.30-rc6-patched
>> 1048576+0 records in
>> 1048576+0 records out
>> 17179869184 bytes (17 GB) copied, 206.465 seconds, 83.2 MB/s
>>
>> Sequential read performance on a big file was improved.
>> Please merge my patch.
>
>I guess the improvement depend on readahead window size.
>Have you mesure random access workload?

I tried with iozone. But there was no difference.

>
>>
>> Thanks.
>>
>> Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
>>
>> diff -Nrup linux-2.6.30-rc6.org/mm/readahead.c
>linux-2.6.30-rc6.unplug/mm/readahead.c
>> --- linux-2.6.30-rc6.org/mm/readahead.c 2009-05-18 10:46:15.000000000 +0900
>> +++ linux-2.6.30-rc6.unplug/mm/readahead.c 2009-05-18 13:00:42.000000000 +0900
>> @@ -490,5 +490,7 @@ page_cache_async_readahead(struct addres
>>
>> /* do read-ahead */
>> ondemand_readahead(mapping, ra, filp, true, offset, req_size);
>> +
>> + blk_run_backing_dev(mapping->backing_dev_info, NULL);
>> }
>> EXPORT_SYMBOL_GPL(page_cache_async_readahead);
>>
>> --
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