Alexander Motin wrote: > Julian Elischer wrote: >> In the Fusion-io driver we find that the limiting factor is not the >> size of MAXPHYS, but the fact that we can not push more than >> 170k tps through geom. (in my test machine. I've seen more on some >> beefier machines), but that is only a limit on small transacrtions, >> or in the case of large transfers the DMA engine tops out before a >> bigger MAXPHYS would make any difference. > > Yes, GEOM is quite CPU-hungry on high request rates due to number of > context switches. But impact probably may be reduced from two sides: by > reducing overhead per request, or by reducing number of requests. Both > ways may give benefits. > > If common opinion is not to touch defaults now - OK, agreed. (Note, > Scott, I have agreed :)) But returning to the original question, does > somebody knows real situation when increased MAXPHYS still causes > problems? At least to make it safe. well I know we havn't tested our bsd driver yet with MAXPHYS > 128KB at this time.. Must try that some time :-)Received on Sun Mar 21 2010 - 14:46:57 UTC
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