convert RecordIO to pwritev
convert RecordIO to pwritev

Summary: zero-copy

Test Plan: record_io_test

Reviewed By: lucian@fb.com

FB internal diff: D806813

wildinto/folly,upsoft/folly,SammyK/folly,romange/folly,xzmagic/folly,tomhughes/folly,leolujuyi/folly,cppfool/folly,rklabs/folly,clearlylin/folly,PPC64/folly,SeanRBurton/folly,facebook/folly,clearlinux/folly,rklabs/folly,PPC64/folly,Orvid/folly,bowlofstew/folly,chjp2046/folly,clearlylin/folly,nickhen/folly,hongliangzhao/folly,unmeshvrije/C--,KSreeHarsha/folly,upsoft/folly,sakishum/folly,kernelim/folly,clearlylin/folly,Hincoin/folly,mqeizi/folly,xzmagic/folly,ykarlsbrun/folly,tomhughes/folly,yangjin-unique/folly,unmeshvrije/C--,sakishum/folly,SammyK/folly,lifei/folly,charsyam/folly,gaoyingie/folly,Hincoin/folly,bowlofstew/folly,brunomorishita/folly,gavioto/folly,facebook/folly,alexst07/folly,floxard/folly,tempbottle/folly,constantine001/folly,nickhen/folly,tempbottle/folly,PPC64/folly,kernelim/folly,colemancda/folly,colemancda/folly,unmeshvrije/C--,Hincoin/folly,shaobz/folly,constantine001/folly,CJstar/folly,gaoyingie/folly,kernelim/folly,reddit/folly,Eagle-X/folly,bobegir/folly,project-zerus/folly,alexst07/folly,colemancda/folly,cppfool/folly,loverszhaokai/folly,wildinto/folly,guker/folly,fw1121/folly,guker/folly,sonnyhu/folly,cole14/folly,rklabs/folly,lifei/folly,chjp2046/folly,reddit/folly,floxard/folly,cppfool/folly,mqeizi/folly,xzmagic/folly,zhiweicai/folly,cole14/folly,renyinew/folly,raphaelamorim/folly,shaobz/folly,mqeizi/folly,sonnyhu/folly,yangjin-unique/folly,charsyam/folly,rklabs/folly,project-zerus/folly,arg0/folly,fw1121/folly,PPC64/folly,guker/folly,tempbottle/folly,xzmagic/folly,yangjin-unique/folly,hongliangzhao/folly,bsampath/folly,clearlinux/folly,SammyK/folly,yangjin-unique/folly,Orvid/folly,sakishum/folly,bsampath/folly,loversInJapan/folly,mqeizi/folly,cole14/folly,bikong2/folly,bobegir/folly,shaobz/folly,clearlinux/folly,reddit/folly,floxard/folly,bowlofstew/folly,wildinto/folly,hongliangzhao/folly,bikong2/folly,lifei/folly,theiver9827/folly,raphaelamorim/folly,zhiweicai/folly,zhiweicai/folly,bobegir/folly,PPC64/folly,loversInJapan/folly,arg0/folly,lifei/folly,bikong2/folly,bowlofstew/folly,colemancda/folly,ykarlsbrun/folly,cole14/folly,bikong2/folly,gavioto/folly,project-zerus/folly,juniway/folly,fw1121/folly,fw1121/folly,loverszhaokai/folly,chjp2046/folly,juniway/folly,cole14/folly,reddit/folly,SammyK/folly,clearlinux/folly,juniway/folly,PoisonBOx/folly,charsyam/folly,xzmagic/folly,renyinew/folly,charsyam/folly,KSreeHarsha/folly,bowlofstew/folly,juniway/folly,loverszhaokai/folly,floxard/folly,nickhen/folly,constantine001/folly,floxard/folly,raphaelamorim/folly,guker/folly,arg0/folly,facebook/folly,KSreeHarsha/folly,sakishum/folly,upsoft/folly,KSreeHarsha/folly,bikong2/folly,PoisonBOx/folly,bsampath/folly,project-zerus/folly,renyinew/folly,stonegithubs/folly,tomhughes/folly,PoisonBOx/folly,theiver9827/folly,guker/folly,wildinto/folly,SeanRBurton/folly,Eagle-X/folly,Orvid/folly,upsoft/folly,mqeizi/folly,facebook/folly,doctaweeks/folly,loverszhaokai/folly,theiver9827/folly,constantine001/folly,juniway/folly,doctaweeks/folly,brunomorishita/folly,facebook/folly,gavioto/folly,stonegithubs/folly,alexst07/folly,Eagle-X/folly,Eagle-X/folly,gaoyingie/folly,brunomorishita/folly,tomhughes/folly,gavioto/folly,colemancda/folly,bsampath/folly,clearlylin/folly,Hincoin/folly,nickhen/folly,PoisonBOx/folly,tempbottle/folly,doctaweeks/folly,wildinto/folly,ykarlsbrun/folly,SeanRBurton/folly,SeanRBurton/folly,clearlinux/folly,unmeshvrije/C--,ykarlsbrun/folly,KSreeHarsha/folly,constantine001/folly,alexst07/folly,romange/folly,arg0/folly,loversInJapan/folly,Orvid/folly,doctaweeks/folly,alexst07/folly,leolujuyi/folly,cppfool/folly,fw1121/folly,sonnyhu/folly,leolujuyi/folly,renyinew/folly,CJstar/folly,romange/folly,cppfool/folly,gaoyingie/folly,theiver9827/folly,hongliangzhao/folly,sonnyhu/folly,bsampath/folly,romange/folly,chjp2046/folly,shaobz/folly,rklabs/folly,gaoyingie/folly,gavioto/folly,kernelim/folly,yangjin-unique/folly,stonegithubs/folly,ykarlsbrun/folly,arg0/folly,Orvid/folly,romange/folly,leolujuyi/folly,loversInJapan/folly,theiver9827/folly,sonnyhu/folly,bobegir/folly,loverszhaokai/folly,CJstar/folly,lifei/folly,PoisonBOx/folly,bobegir/folly,chjp2046/folly,shaobz/folly,leolujuyi/folly,SeanRBurton/folly,renyinew/folly,raphaelamorim/folly,stonegithubs/folly,CJstar/folly,CJstar/folly,stonegithubs/folly,zhiweicai/folly,loversInJapan/folly,sakishum/folly,clearlylin/folly,unmeshvrije/C--,SammyK/folly,doctaweeks/folly,nickhen/folly,tomhughes/folly,hongliangzhao/folly,reddit/folly,zhiweicai/folly,brunomorishita/folly,Eagle-X/folly,tempbottle/folly,raphaelamorim/folly,brunomorishita/folly,project-zerus/folly,Hincoin/folly,kernelim/folly,unmeshvrije/C--,upsoft/folly