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A comment on The Linux kernel's inability to gracefully handle low memory pressure. Parent comment

Re:The Linux kernel's inability to gracefully handle low mem... by caf on Tuesday August 06, 2019 @08:21PM (#20630953)
Reading large files using direct IO defeats kernel read-ahead, which means you have to take on the complexity of reimplementing it in userspace, or the performance hit of not having it.

This is a good reason for programs to use buffered IO even when they are reading a large file once, so yes my comment was entirely on point.

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Re:The Linux kernel's inability to gracefully handle low mem... by paulsutter on Wednesday August 07, 2019 @11:52AM (#20635830)
Your comments were misleading, even if you want to argue they were on point. I know that you're knowledgable about the kernel, I ready your other comments. The following comments are just not true, except in bizarro world where all code must be in the kernel:

- "Readahead... needs to be buffered"

- "reading unbuffered (ie. O_DIRECT)... you cannot read ahead"

Good application code needs to work around kernel limitations all the time. Your suggestion of fadvise is reasonable, except in practice fadvise rarely makes a measurable difference. The only way to get what you really want is to code it the way you want it, and fortunately, there are multiple ways to do that.

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