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Date: Sun, 9 Sep 2012 16:14:01 -0400 From: Rich Felker <dalias@...ifal.cx> To: musl@...ts.openwall.com Subject: Re: capset() capget() syscalls On Sun, Sep 09, 2012 at 09:04:02PM +0100, Justin Cormack wrote: > On Sat, Sep 8, 2012 at 11:14 PM, Rich Felker <dalias@...ifal.cx> wrote: > > Is there any legitimate user of this horrible API? Last I checked > > these functions were only useful for block-aligned IO on block devices > > and the impression I got was that they were designed solely for > > Oracle's use. (puke) I suppose they could be useful for FUSE drivers > > too, however. We can add them if they have legitimate software that > > needs them. > > It is still the only way to get decent io performance out of an SSD as > far as I can see, being about a factor of 8 faster than anything else > for random reads eg posix aio. Assuming of course our reads are block > aligned. If the normal Linux block cache system is even 25% slower than low-level IO on the device without any operating system at all, that's a major bug they need to fix. Adding hideous APIs to for userspace apps to do their own low-level IO is not a solution. 8x is just atrocious. Where does that figure come from? In fairness, if you're comparing to POSIX aio, that's a pretty bad API too. A thread performing standard blocking pread/pwrite should give the ideal performance. Rich
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