On Thu, 23 Jan 2025, Chuck Lever wrote: > On 1/21/25 10:54 PM, NeilBrown wrote: > > > > The nfsd filecache currently uses list_lru for tracking files recently > > used in NFSv3 requests which need to be "garbage collected" when they > > have becoming idle - unused for 2-4 seconds. > > > > I do not believe list_lru is a good tool for this. It does no allow the > > timeout which filecache requires so we have to add a timeout mechanism > > which holds the list_lru for while the whole list is scanned looking for > > entries that haven't been recently accessed. When the list is largish > > (even a few hundred) this can block new requests which need the lock to > > remove a file to access it. > > > > This patch removes the list_lru and instead uses 2 simple linked lists. > > When a file is accessed it is removed from whichever list it is one, > > then added to the tail of the first list. Every 2 seconds the second > > list is moved to the "freeme" list and the first list is moved to the > > second list. This avoids any need to walk a list to find old entries. > > > > These lists are per-netns rather than global as the freeme list is > > per-netns as the actual freeing is done in nfsd threads which are > > per-netns. > > > > This should not be applied until we resolve how to handle the > > race-detection code in nfsd_file_put(). However I'm posting it now to > > get any feedback so that a final version can be posted as soon as that > > issue is resolved. > > > > Thanks, > > NeilBrown > > > > > > [PATCH 1/4] nfsd: filecache: use nfsd_file_dispose_list() in > > [PATCH 2/4] nfsd: filecache: move globals nfsd_file_lru and > > [PATCH 3/4] nfsd: filecache: change garbage collection list > > [PATCH 4/4] nfsd: filecache: change garbage collection to a timer. > > Hi Neil - > > I would like Dave Chinner to chime in on this approach. When you > resend, please Cc: him. Thanks! Sure, I can do that. But why Dave in particular? I would like to add a comment to the cover letter explaining to Dave what he was added to see and I don't know what to say. Thanks, NeilBrown
