On Thursday 21 February 2008 16:07, David Howells wrote:Thanks for the excellent ascii art, that cleared up the confusion right away. Trying to see if you are offering enough of a win to justify testing it, and if that works out, then going shopping for a bin of rotten vegetables to throw at your design, which I hope you will perceive as useful. In short I am looking for a reason to throw engineering effort at it. From the numbers you have posted I think you are missing some basic efficiencies that could take this design from the sorta-ok zone to wow! I think you may already be in the wow zone for taking load off a server and I know of applications where an NFS server gets hammered so badly that having the client suck a little in the unloaded case is a price worth paying. But the whole idea would be much more attractive if the regressions were smaller. But looking up the object in the cache should be nearly free - much less than a microsecond per block. If not then there are design issues. I suspect that you are doing yourself a disservice by going all the way through the vfs to do this cache lookup, but this needs to be proved. Double caching and vm unawareness of that has to hurt. So without the persistent cache it can omit the LOOKUP and just send the filehandle as part of the READ? Doesn't that just mean you have to preload the lookup table for the persistent cache so you can determine whether you are caching the data for a filehandle without going to disk? Ah I should have read ahead. I think the correct answer is "a lot". Your big can-t-get-there-from-here is the round trip to the server to determine whether you should read from the local cache. Got any ideas? And where is the Trond-meister in all of this? Regards, Daniel - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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