Date: Sat, 23 Feb 2002 08:55:14 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> Cc: arch@FreeBSD.org Subject: Re: reclaiming v_data of free vnodes Message-ID: <3C77C972.598B4181@mindspring.com> References: <200202231556.g1NFu9N9040749@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp>
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Seigo Tanimura wrote: > which is almost the same as the number of the total vnodes. (in > cvsup.jp.FreeBSD.org, almost all in-use vnodes are actually inodes) > > This seems due to vrele() and vput() not calling VOP_RECLAIM(). One > solution is to always reclaim a vnode in vrele()/vput(), while we can > also run a kernel thread to scan the free vnodes and reclaim some of > them. Which one would be better, or are there any other ways? > > Any comments are welcome. Taking the first quoted sentence, above, into account, it seems that the SVR4 approach of giving the vnode tot the FS to manage, instead of using a system wide pool, would be the best approach. That way the vnode and in core inode allocation are combined (in fact, probably the same "malloc"). It also inherently parallelizes allocation when two or more FS's are in use, which in turn starts to work around one of the big problems facing the concurrency push-down in SMPng. The ihash cache really needs to go away -- or at least, it needs to keep the page associations, so that clean pages that are in core don't get faulted in again because of a disassociated vnode/inode pair when the inode is reclaimed. This is also at the root of your problem, where there is no explicit reclaim possible because the vnode and inode are not tightly coupled: you can free resources used by one and not the other, but have no way to reclaim the relationship from the vnode dise (the inode side can reclaim the relationship, but loses the cached page associations). Frankly, it makes sense to me, even if the system retains ownership of the vnode, to find a way to pass the vput/vrele notification to the VFS via a VOP_VRELE (or something similar), so that there is explicit notification. THis is pretty much a requirement for more than trivial stacking, at some point, unless you want to greatly complicate each of the stacking layers. Combining would also help in the nfsnode cases, I think. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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