On 07/30/2011 10:34 PM, Dave Chinner wrote: > On Fri, Jul 29, 2011 at 05:44:19PM +0400, Glauber Costa wrote: >> This patch introduces a simple generic vfs option parser. >> Right now, the only option we have is to limit the size of the dcache. >> >> So any user that wants to have a dcache entries limit, can specify: >> >> mount -o whatever_options,vfs_dcache_size=XXX<dev> <mntpoint> >> >> It is supposed to work well with remounts, allowing it to change >> multiple over the course of the filesystem's lifecycle. >> >> I find mount a natural interface for handling filesystem options, >> so that's what I've choosen. Feel free to yell at it at will if >> you disagree. > > IMO, the whole point of having a configurable cache size maximum is > that is can be changed at runtime. Tying it to mount options is a > painful way to acheive that because the only way to change it would > be via a remount command. And what's wrong with a remount command? It's a quite natural operation. Furthermore, changing it at runtime is important - and as you noted, quite doable, but it is not "the whole point of it". The whole point of it is to allow a piece of the fs hierarchy to have a limit on the cache sizes. So I expect the most common usage to be at mount itself. Specifically for the use case I have in mind, when a new container is created. > I'm not sure what the best API is, but I'd prefer something that is > specific to a superblock, not a vfs mount. Perhaps something in > /sys/fs? I am not sure either, but I still believe my proposal is superior to write-to-a-file specifically. Writing to a file, be it in proc, sys, or wherever, leaves a window of opportunity open between mounting a filesystem and limiting its caches. Doing it on mount is atomic. Effectively, I see this limit as a property of a particular instance of a mounted filesystem. Since all properties of a filesystem are specified during mount, this becomes a natural extension. Let me know what you think _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
