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ͦͷ IONICE, ΄Μͱʹޮ͍ͯ·͔͢ʁ TAKAMURA Narimichi @nari_ex hbstudy-2014-08-14

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what is ionice ? I/O ͷॲཧ༏ઌ౓Λࢦఆ͢ΔLinuxίϚϯυ nice ίϚϯυͷ I/O όʔδϣϯ nice ίϚϯυͰ͸ I/O ༏ઌ౓Λ੍ޚෆՄ

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I/O ༏ઌ౓Ϋϥε RT ( Real-time ) ࠷ߴ༏ઌ౓ BE ( Best-Effort ) σϑΥϧτ༏ઌ౓ Idle ࠷௿༏ઌ౓

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BE: Ϋϥε಺༏ઌ౓ BE ΫϥεͷΈɺΫϥε಺༏ઌ౓͕͋Δ ༏ઌ౓͸ 0ʙ7 ·Ͱͷ 8ஈ֊ 0͕࠷ߴ༏ઌ౓ɺ7͕࠷௿༏ઌ౓ ༏ઌ౓͸Ϋϥεͷ࿮Λ௒͑ͳ͍ RT > BE (0) IDLE < BE (7)

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How to ionice RT ΫϥεΛࢦఆ: ionice -c1 BE ΫϥεΛࢦఆ: ionice -c2 -n <0ʙ7> IDLE ΫϥεΛࢦఆ: ionice -c3

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༨ஊ: nice ίϚϯυ Ϋϥε͸ͳ͍ ༏ઌ౓ ( nice஋ ) ͸ -20ʙ19 -20 ͕࠷ߴ༏ઌ౓ɺ19͕࠷௿༏ઌ౓

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ෛՙΛ࠷খݶʹ཈͍͑ͨʂ

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ionice, nice Λۦ࢖ͯ͠…

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# ionice -c3 nice -n19

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͜ΕͰ׬ᘳͩʂʂʂ

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ͪΐͬͱ·ͬͯ

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ͦͷ IONICE, ΄Μͱʹޮ͍ͯ·͔͢ʁ

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ionice ͕ޮ͘৚݅ I/O εέδϡʔϥ ReadͳͷʁWriteͳͷʁϑϥά͸ʁ ϑΝΠϧ࡞੒ϑϥά Ωϟογϡͷ༗ແ

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I/O Scheduler…

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VFS Χʔωϧۭؒ γεςϜίʔϧ Ϣʔβۭؒ ෺ཧ σόΠε ϑΝΠϧγεςϜ σΟεΫΩϟογϡ ൚༻ϒϩοΫ૚ ෺ཧ σόΠε ϓϩηε I/Oεέδϡʔϥ૚ σόΠε υϥΠό σόΠε υϥΠό

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৚݅ͦͷ̍: I/O Scheduler(1) CFQ εέδϡʔϥҎ֎͸ແཧ Linux ඪ४ͷεέδϡʔϥ͸ CFQ Amazon Linux ͸ Noop ͳͷͰ஫ҙ Unbreakable Linux ͸ Deadline ͳ ͷͰ஫ҙ

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σόΠεͻͱͭʹI/Oεέδϡʔϥͻͱͭ σόΠεΛ·͙ͨॲཧͷ৔߹ʹ஫ҙ ॲཧʹؔΘΔ͢΂ͯͷσόΠεΛ֬ೝͤΑ # cat /sys/block//queue/ scheduler ৚݅ͦͷ̍: I/O Scheduler(2)

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৚݅ͦͷ̎: I/Oॲཧͷ಺༰(1) Write() ͸جຊతʹޮ͔ͳ͍ O_DIRECT, O_SYNC Λϑϥάཱͯ ͯΕ͹OK -o sync ͰϚ΢ϯτ͞ΕͨϑΝΠϧ γεςϜͳΒOK

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৚݅ͦͷ̎: I/Oॲཧͷ಺༰(2) Read() ΋͢΂ͯʹޮ͘Θ͚Ͱ͸ͳ͍ σΟεΫΩϟογϡ͕͋Δͱμϝ σΟεΫΞΫηεͳ͍͔Β౰વ

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·ͱΊ ionice ͸ҎԼͷ ̎৚݅Λຬͨͨ࣌͠ʹͪΌΜͱಈ͘ I/O Scheduler ͕ CFQ ಛఆͷI/Oॲཧ Ωϟογϡ͞Ε͍ͯͳ͍ϑΝΠϧ΁ͷRead ಛघϑϥάͷཱͬͨ Write

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͍͞͝ʹ man ioprio_set Λಡ΋͏ ϑΝΠϧ࡞੒ϑϥάͷࡉ͔͍͜ͱ͸·ͨࠓ౓ O_SYNC, O_DSYNC, O_FSYNC… ionice -p Λ࢖͏ͱɺىಈதͷϓϩη εͷI/O༏ઌ౓มߋͰ͖ΔΑ