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From: Jeff Furlong <jeff.furlong@wdc.com>
To: "fio@vger.kernel.org" <fio@vger.kernel.org>
Subject: fio offset with ba
Date: Fri, 20 Oct 2017 19:08:39 +0000	[thread overview]
Message-ID: <BN3PR0401MB145727ED714B57825C91A8E78F430@BN3PR0401MB1457.namprd04.prod.outlook.com> (raw)

Hi All,
I don't quite follow the logic in the calculate offset function.  The offset parameter recently allows a percentage.  Suppose we set it to 50% and want to block align the IO's starting at 50% of device capacity, then block aligned to 8KB.

# fio -version
fio-3.1-60-g71aa

# blockdev --getsize64 /dev/nvme1n1
3200631791616

# fio --name=test_job --ioengine=libaio --direct=1 --rw=read --iodepth=1 --size=100% --bs=4k --filename=/dev/nvme1n1 --runtime=1s --offset=50% --log_offset=1 --write_iops_log=test_job --ba=8k

# cat test_job_iops.1.log
0, 1, 0, 4096, 1600315895808
0, 1, 0, 4096, 1600315899904
0, 1, 0, 4096, 1600315904000
0, 1, 0, 4096, 1600315908096

So we can see the device has 3200631791616 bytes, 50% of which is 1600315895808 bytes, which happens to be 4KB aligned, but not 8KB aligned.  Even though we set the --ba=8k parameter, the offset LBA as logged in the iops.1.log shows 4KB alignment.  Does --ba work for all IO's or only random IO's?  If all, does get_start_offset() control the raw offset value?  I don't see why the min(ba, bs) is used in the calculation, but perhaps I am missing something.  Thanks.

Regards,
Jeff


             reply	other threads:[~2017-10-20 19:08 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-20 19:08 Jeff Furlong [this message]
2017-10-20 21:01 ` fio offset with ba Sitsofe Wheeler
2017-10-21  0:13   ` Jeff Furlong
2017-10-21  4:21     ` Sitsofe Wheeler
2017-10-23 23:56       ` Jeff Furlong
2017-10-24  6:21         ` Sitsofe Wheeler
2017-10-26  0:27           ` Jeff Furlong
2017-10-26  4:24             ` Jens Axboe
2017-10-26  6:27               ` Sitsofe Wheeler
2017-10-26 14:25                 ` Jens Axboe

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