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Parameter directio and dsync can't prevent from writing in the buffer? #124
Description
I'm using filebench to test performance of ceph.
I map the image of rbd to device and mount the device to local directory, and i use aiowrite to test. My configure is following:
set $dir=rbdmap/rbdmap0
set $bytes=100g
set $filesize=100g
set $iosize=4m
set $iters=1
set $nthreads=1
define file name=bigfile1,path=$dir,size=$filesize,prealloc,reuse
define process name=filewriter,instances=1
{
thread name=filewriterthread,instances=$nthreads
{
flowop aiowrite name=write-file,filename=bigfile1,random,dsync,iosize=$iosize,iters=$iters,directio
flowop finishonbytes name=finish,value=$bytes
}
}
run 300
I set the parameter directio and dsync but when i run the test, my memory is used about 100G, and the bw is almost 25GB/s, i think data is written into memory and slowly flush into the device.
I want to ask how to set non-buffered and test accurate result?
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