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On Tue, Dec 07 2004, Andrew Morton wrote: > Andrea Arcangeli <andrea@suse.de> wrote: > > > > The desktop is ok with "as" simply because it's > > normally optimal to stop writes completely > > AS doesn't "stop writes completely". With the current settings it > apportions about 1/3 of the disk's bandwidth to writes. > > This thing Jens has found is for direct-io writes only. It's a bug. Indeed. It's a special case one, but nasty for that case. > The other problem with AS is that it basically doesn't work at all with a > TCQ depth greater than four or so, and lots of people blindly look at > untuned SCSI benchmark results without realising that. If a distro is That's pretty easy to fix. I added something like that to cfq, and it's not a lot of lines of code (grep for rq_in_driver and cfq_max_depth). > always selecting CFQ then they've probably gone and deoptimised all their > IDE users. Andrew, AS has other issues, it's not a case of AS always being faster at everything. > AS needs another iteration of development to fix these things. Right now > it's probably the case that we need CFQ or deadline for servers and AS for > desktops. That's awkward. Currently I think the time sliced cfq is the best all around. There's still a few kinks to be shaken out, but generally I think the concept is sounder than AS. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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