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Rev

Thanks. I noticed if I issue the dd command again with the same arguments，it wont get the cached number that's returned by free command increased despite the execution of sync command. Is this because the page cache hit？

Jepsenwan
– Jepsenwan

2017-07-12 03:55:24 +00:00
Commented Jul 12, 2017 at 3:55
Yes. Caches are not dropped until there is not enough free memory for other demands.

John Mahowald
– John Mahowald

2017-07-12 10:47:30 +00:00
Commented Jul 12, 2017 at 10:47
Thanks John. An extra question.Under any circumstance the hugepage will be employed as page cache? For instance, in system running a Oracle database.

Jepsenwan
– Jepsenwan

2017-07-13 10:13:35 +00:00
Commented Jul 13, 2017 at 10:13
Huge pages cannot be used as as page cache or a few other uses, no. Which means tuning for databases involves sizing pages correctly. This is a broad topic and really a different question, I recommend reading a tuning guide for that database.

John Mahowald
– John Mahowald

2017-07-13 13:15:58 +00:00
Commented Jul 13, 2017 at 13:15
Thanks John. I just realized that the hugepage is much bigger than page in disk. Besides. Hugepage is pined in main memory. So it wont have anything to do with page cache.

Jepsenwan
– Jepsenwan

2017-07-13 13:35:07 +00:00
Commented Jul 13, 2017 at 13:35

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