Messages in this thread | | | Date | Fri, 19 Mar 2004 11:30:16 +0100 | From | Takashi Iwai <> | Subject | Re: CONFIG_PREEMPT and server workloads |
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At Thu, 18 Mar 2004 22:10:06 -0800, Andrew Morton wrote: > > Takashi Iwai <tiwai@suse.de> wrote: > > > > BTW, i had the worst latency in sis900's timer handler. > > it takes 3ms, and hard to fix, too :-< > > It's all coming back to me now. > > The worst-case latency is during umount, fs/inode.c:invalidate_list() when > the filesystem has a zillion inodes in icache. Measured 250 milliseconds > on a 256MB 2.7GHz P4 here. OK, so don't do that.
also that's not included in my test case :)
> The unavoidable worst case is in the RCU callbacks for dcache shrinkage - > I've seen 25 millisecond holdoffs on the above machine during filesystem > stresstests when RCU is freeing a huge number of dentries in softirq > context.
hmm, this wasn't also evaluated in my tests. it's worthy to try. thanks for the info.
> This if Hard To Fix. Dipankar spent quite some time looking into it and > had patches, but I lost track of where they're at.
couldn't this tasklet be replaced with workqueue or such?
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