Stefan Priebe - Profihost AG posted on Mon, 09 May 2016 14:59:25 +0200 as excerpted:
> Am 03.05.2016 um 00:05 schrieb Omar Sandoval: >> On Fri, Apr 29, 2016 at 10:48:15PM +0200, Stefan Priebe wrote: >>> just want to drop a note that all those ENOSPC msg are gone with v4.5 >>> and space_cache=v2. Any plans to make space_cache=v2 default? >>> >> Yup, we want to make space_cache=v2 the default at some point. I'm >> running it on my own machines and testing it here at Facebook and >> haven't run into any issues yet. Besides stability, I also want to make >> sure there aren't any performance regressions versus the old free space >> cache that we haven't thought about yet. >> >> Thanks for trying it out :) > > Can i patch v2 as a default for me? I just looked at the code but didn't > find an easy way to make v2 the default. Based on previous posts, space_cache=v2 will rewrite the cache to tree form, and it'll stay that way (thus your default) until you specifically use the clear-cache option. IOW, the code detects existing v1 or v2 and continues to use it until a clear-cache mount and no v2 set on the mount after, to switch back to v1, or a space_cache=v2 to switch to it. IOW, the space_cache option doesn't need set more than once (and for v1, it doesn't actually need set at all, except perhaps after a clear_cache, I've never specifically set space_cache here, but it's always listed in the mount output and /proc/self/mounts). After that it carries on the way it was. Or did you mean that you're creating enough new btrfs that using space_cache=v2 even once is difficult, and you'd like to patch it to use v2 from the get-go? Presumably that can indeed be patched in, but not being a dev, even if I could figure out a patch that worked for it, there's a fair chance it would be more a hack than proper code. (As an admin I have a patch that switches the normal relatime default to noatime, so I don't have to have it in all my fstab entries, etc, and it works, but it's clearly a hack compared to what a proper dev would code.) -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
