Date: Wed, 28 Oct 2015 14:04:59 +0100 From: [Jacek Wielemborek](https://github.com/d33tah) Subject: pv performance improvements: direct I/O and POSIX_FADV_SEQUENTIAL? Hi, I was exploring a performance problem I was having with my system today and found that it's most likely that the Linux kernel caches a big files that "pv" reads and drops important cached files that have to be re-read later. I read up on a solution and found that pv could use some direct I/O support, so that if a file is too big, it doesn't overwrite all cache. Also, posix_fadvise(infile_fd, POSIX_FADV_SEQUENTIAL, 0, 0); could perhaps add a speedup - that's what I found in "cat" source code. What do you think? ---- Date: Mon, 9 Nov 2015 22:42:24 +0000 From: Andrew Wood To: Jacek Wielemborek Subject: Re: pv performance improvements: direct I/O and POSIX_FADV_SEQUENTIAL? Thanks for the suggestions. I already use the cache loading side effect of PV to show a progress bar while certain large files are pre-cached - I think you're right to suggest an option to turn this off by using direct I/O. I'd not heard of the posix_fadvise() function and will look into it. It sounds like a good idea, I just need to make sure that any code I add is portable to all the systems PV currently runs on.