Because we should keep the logic of journal write thread simple. It performs better in pcie ssd. But I think the strategy you mentioned above is good for hdd or sata ssd.
2015-11-20 17:16 GMT+08:00 池信泽 <xmdx...@gmail.com>: > Yes, You are right. But in ceph master branch, we have already > prepare_entry(add padding) before sumibt_entry. If you have good idea > base on this, > It would be great. > > 2015-11-20 17:12 GMT+08:00 changtao381 <changtao...@163.com>: >> Hi All, >> >> Thanks for you apply! >> >> If directioIO + async IO requirement that alignment, it shouldn't aligned by >> PAGE for each journal entry. >> For it may write many entries of journal once time >> >> So it should do alignment after [prepare_multi_write] rather than do it each >> in [prepare_single_write] ? Am I right? >> >> -----邮件原件----- >> 发件人: piotr.da...@ts.fujitsu.com [mailto:piotr.da...@ts.fujitsu.com] >> 发送时间: 2015年11月20日 16:42 >> 收件人: changtao381; ceph-devel@vger.kernel.org >> 主题: RE: journal alignment >> >>> -----Original Message----- >>> From: ceph-devel-ow...@vger.kernel.org [mailto:ceph-devel- >>> ow...@vger.kernel.org] On Behalf Of changtao381 >>> Sent: Friday, November 20, 2015 9:33 AM >>> >>> HI All, >>> >>> Why it is needed an entry of journal t is aligned by CEPH_PAGE_MASK ? For >>> it causes the data of journal write are amplified by 2X for small io >>> >>> For example write io size 4096 bytes, it may write 8192 bytes >>> >>> prepare_single_write 2 will write 98304 : seq 24 len 4324 -> 8192 (head 40 >>> pre_pad 0 ebl 4324 post_pad 3788 tail 40) (ebl alignment -1) >>> >>> Thanks! >> >> It is a direct-IO+async IO requirement (writing on page-size boundary which >> is incidentally also a multiply of sector size). >> >> With best regards / Pozdrawiam >> Piotr Dałek >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >> the body of a message to majord...@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > -- > Regards, > xinze -- Regards, xinze -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
