Re: How can we make page replacement smarter (was: swap-prefetch)

2007-07-28 Thread Rik van Riel
Al Boldi wrote: Chris Snook wrote: At best, reads can be read-ahead and cached, which is why sequential swap-in sucks less. On-demand reads are as expensive as I/O can get. Which means that it should be at least as fast as swap-out, even faster because write to disk is usually slower than

Re: How can we make page replacement smarter (was: swap-prefetch)

2007-07-28 Thread Robert Hancock
Al Boldi wrote: Chris Snook wrote: Al Boldi wrote: Because it is hard to quantify the expected swap-in speed for random pages, let's first tackle the swap-in of consecutive pages, which should be at least as fast as swap-out. So again, why is swap-in so slow? If I'm writing 20 pages to swap,

Re: How can we make page replacement smarter (was: swap-prefetch)

2007-07-28 Thread Al Boldi
Chris Snook wrote: > Al Boldi wrote: > > Because it is hard to quantify the expected swap-in speed for random > > pages, let's first tackle the swap-in of consecutive pages, which should > > be at least as fast as swap-out. So again, why is swap-in so slow? > > If I'm writing 20 pages to swap, I

Re: How can we make page replacement smarter (was: swap-prefetch)

2007-07-28 Thread Chris Snook
Al Boldi wrote: Chris Snook wrote: Resource size has been outpacing processing latency since the dawn of time. Disks get bigger much faster than seek times shrink. Main memory and cache keep growing, while single-threaded processing speed has nearly ground to a halt. In the old days, it made

Re: How can we make page replacement smarter (was: swap-prefetch)

2007-07-28 Thread Chris Snook
Al Boldi wrote: Chris Snook wrote: Resource size has been outpacing processing latency since the dawn of time. Disks get bigger much faster than seek times shrink. Main memory and cache keep growing, while single-threaded processing speed has nearly ground to a halt. In the old days, it made

Re: How can we make page replacement smarter (was: swap-prefetch)

2007-07-28 Thread Al Boldi
Chris Snook wrote: Al Boldi wrote: Because it is hard to quantify the expected swap-in speed for random pages, let's first tackle the swap-in of consecutive pages, which should be at least as fast as swap-out. So again, why is swap-in so slow? If I'm writing 20 pages to swap, I can find

Re: How can we make page replacement smarter (was: swap-prefetch)

2007-07-28 Thread Robert Hancock
Al Boldi wrote: Chris Snook wrote: Al Boldi wrote: Because it is hard to quantify the expected swap-in speed for random pages, let's first tackle the swap-in of consecutive pages, which should be at least as fast as swap-out. So again, why is swap-in so slow? If I'm writing 20 pages to swap,

Re: How can we make page replacement smarter (was: swap-prefetch)

2007-07-28 Thread Rik van Riel
Al Boldi wrote: Chris Snook wrote: At best, reads can be read-ahead and cached, which is why sequential swap-in sucks less. On-demand reads are as expensive as I/O can get. Which means that it should be at least as fast as swap-out, even faster because write to disk is usually slower than

How can we make page replacement smarter (was: swap-prefetch)

2007-07-27 Thread Al Boldi
Chris Snook wrote: > Resource size has been outpacing processing latency since the dawn of > time. Disks get bigger much faster than seek times shrink. Main memory > and cache keep growing, while single-threaded processing speed has nearly > ground to a halt. > > In the old days, it made lots of

How can we make page replacement smarter (was: swap-prefetch)

2007-07-27 Thread Al Boldi
Chris Snook wrote: Resource size has been outpacing processing latency since the dawn of time. Disks get bigger much faster than seek times shrink. Main memory and cache keep growing, while single-threaded processing speed has nearly ground to a halt. In the old days, it made lots of sense