Messages in this thread |  | | From | "Dan Maas" <> | Subject | Re: Swap | Date | Tue, 20 Nov 2001 16:26:57 -0500 |
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> I bet they're getting mmap()d, like all mp3 programs seem to do
Just a note here - I see much fewer buffer underruns and more consistent read-ahead/drop-behind behavior (i.e. no paging of other programs) when using plain read(), as opposed to mmap(). This is in a video playback program that pumps 3.6MB/sec!
MP3 datarates are less than 50KB/sec, so I don't really see why they stand to benefit from mmap()... With mmap() you pay the extra cost of setting up/tearing down the mapping, and the kernel->user copy is virtually insignificant anyway (you already are paying for a single copy plus cache pollution when moving the data from filesystem buffer to sound card DMA buffer, so a second copy isn't a big deal)...
Regards, Dan
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