On Sat, Apr 4, 2015 at 11:18 AM, Alexander Motin <[email protected]> wrote:
> On 04.04.2015 19:08, Matthew Ahrens wrote: > > Strided prefetch: mostly evil. > > > > I've rewritten the predictive prefetcher; new version only detects > > forward sequential streams. Will propose for upstreaming soon. In the > > mean time feel free to check out: > > > > > https://github.com/delphix/delphix-os/commit/13cf8efe4b6b10930b478a15f9de92880bbdd412 > > Ah. Thank you. I haven't tried it yet, but I like some ideas there, > while the rest can probably be justified by simplicity. I just slightly > worry that with your patch single large read does not start prefetch. > Actually I fixed that in some later commits. Will upstream it all together. > From one side that may be counted as correct behavior (request was > indeed only one and we have no idea whether there will be the second), > but if the second request arrive -- cache has nothing for it at all, not > even started. > > Generally I hope "soon" happen sooner then in another six months, > otherwise we could start cutting out strides less aggressively, starting > from my less invasive patch. ;) > I have a dozen reviews out; help review them and I'll be able to get to the prefetch stuff faster :-) > > PS: FreeBSD code style does not recommend inline definition of > variables, that you used several times in your patch. > > No C99 in FreeBSD? I didn't realize that illumos was the only operating system that's updated its language in the past 15 years :-P Personally, I find that reducing variable scope increases readability as well as helps avoid bugs. --matt
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