Messages in this thread | | | Date | Mon, 17 Oct 2005 17:24:00 +0530 | From | Dipankar Sarma <> | Subject | Re: VFS: file-max limit 50044 reached |
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On Sun, Oct 16, 2005 at 07:34:24PM -0700, Linus Torvalds wrote: > On Sun, 16 Oct 2005, Dipankar Sarma wrote: > > > > Linus, I don't think this has anything to do with RCU grace periods > > like we discussed previously. I measured on my 3.6GHz x86_64 and > > found that open()/close() pair on /dev/null takes about 45500 > > cycles or 12 microseconds. [Does that sound resonable?]. > > That sounds very slow. I can do a million open/close pairs in 4 seconds on > a 2.5GHz G5. Maybe you tested a cold-cache case?
I measured after warming up for about a 100 times or so. It is not a cold-cache case. I think we have a bigger problem in hand here. I measured this with 2.6.13 and saw that I could do the same in ~3 microseconds per iteration. It balloons to 12 microseconds in 2.6.14-rc1. I am looking at this right now apart from the other problems.
> I suspect this patch is worth it for the 2.6.14 timeframe, but I'll wait > for confirmation. > > In fact, for 2.6.14, I'd almost do an even more minimal one. I agree with > your changing the file counter to an atomic, but I'd rather keep that > change for later.
Even beyond the file counter issue, we do need to address the DoS and the open/close slowdown issue.
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