Eric Wong <normalper...@yhbt.net> writes: > Måns Rullgård <m...@mansr.com> wrote: >> Eric Wong <normalper...@yhbt.net> writes: >> >> > Eric Wong <normalper...@yhbt.net> wrote: >> >> All relevant audio file formats store data sequentially, so >> >> give a hint to the kernel to perform more readahead. In current >> >> Linux, the readahead hint doubles readahead pages and can help >> >> with playback on slow devices. >> > >> > Btw, I've been running this for a few years, too; but pretty >> > much all on FLAC. >> > >> > I don't know if there's audio formats we support which aren't >> > sequential. Maybe there's some wacky audio format which >> > requires random read all over the place... >> >> I can't think of any format that isn't mostly sequential, certainly not >> that's supported in SoX. There might exist some format that separates >> channel data such that reading sequentially from multiple starting >> points is the best strategy. > > Yeah, I was wondering about something along those lines, > especially if exceeding 2 channels...
I know of formats that interleave channel data in blocks of a few kilobytes, but those don't require seeking. Some MOV/MP4 video files store the video and audio completely separately, but we don't care about those. >> What sort of improvement do you get from this anyway? I'm not opposed >> to the addition, just curious. > > I didn't measure before :x It's more of a "it couldn't hurt" > thing and let the kernel (and configured per-device readahead) > decide. It's only intended as a hint for the kernel, after all. > > My 7200 RPM HDD has 256 MB cache on it; I couldn't measure any > difference even with 'echo 3 >/proc/sys/vm/drop_caches' (Linux) > and reading ~300 MB of stuff before testing in hopes it'd clear > the internal HDD cache. Maybe slower mounts (optical storage, > 4200 RPM HDDs, or network FSes) will see the benefit. > > I used to play audio on a laptop using an sshfs mount back in > the day (with FUSE readahead, too), but haven't had the need or > ability to do that for years, now. Hmm, I prefer not to add code like this on a hunch. Maybe I'll hook up some horrible old laptop drive and see if it makes a difference there. Then again, does anyone care? -- Måns Rullgård _______________________________________________ SoX-devel mailing list SoX-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/sox-devel
