atom feed21 messages in org.freebsd.freebsd-fsRe: Very inconsistent (read) speed on...
FromSent OnAttachments
Lev SerebryakovAug 30, 2011 12:10 pm 
Lev SerebryakovAug 30, 2011 12:17 pm 
Kirk McKusickAug 30, 2011 1:08 pm 
Lev SerebryakovAug 30, 2011 3:13 pm 
Lev SerebryakovAug 30, 2011 3:29 pm 
Lev SerebryakovAug 30, 2011 3:31 pm 
Bob FriesenhahnAug 30, 2011 3:39 pm 
Kirk McKusickAug 30, 2011 4:00 pm 
Jeremy ChadwickAug 30, 2011 5:42 pm 
Daniel KalchevAug 31, 2011 12:10 am 
Lev SerebryakovAug 31, 2011 12:38 am 
Lev SerebryakovAug 31, 2011 1:02 am 
Lev SerebryakovAug 31, 2011 1:10 am 
Lev SerebryakovAug 31, 2011 1:18 am 
Lev SerebryakovAug 31, 2011 1:36 am 
Daniel KalchevAug 31, 2011 1:48 am 
Lev SerebryakovAug 31, 2011 2:03 am 
Jeremy ChadwickAug 31, 2011 3:11 am 
Lev SerebryakovAug 31, 2011 4:36 am 
Daniel KalchevAug 31, 2011 4:46 am 
Lev SerebryakovAug 31, 2011 5:49 am 
Subject:Re: Very inconsistent (read) speed on UFS2
From:Bob Friesenhahn (bfri@simple.dallas.tx.us)
Date:Aug 30, 2011 3:39:44 pm
List:org.freebsd.freebsd-fs

On Wed, 31 Aug 2011, Lev Serebryakov wrote:

I'll try this experiment with mmap() and touching every 4096-th byte of mapped memory instead of read(2).

Strange enough, it gives only 40-50MiB/s and results are very consistent.

It really surprise me. I didn't think, that there will be so much difference, I was sure, that it will be almost equivalent speed.

FreeBSD does not seem to default to sequential read-ahead when memory mapping is used with sequential page access. Try using madvise() with the MADV_SEQUENTIAL option and see if it helps.

There are also MADV_WILLNEED, MADV_DONTNEED, and MADV_FREE. Careful use of these options can help performance quite a lot when data is large compared to memory.

Bob

-- Bob Friesenhahn bfri@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/

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