> 2021年7月16日 00:42，Taylor Blau <me@xxxxxxxxxxxx> 写道： > > On Fri, Jul 16, 2021 at 12:30:18AM +0800, Sun Chao wrote: >> I'm sorry to reply so late, I work long hours during the day, and the >> company network can not send external mail, so I can only go home late >> at night to reply to you. > > There's no need to apologize :-). > >> Thanks for your reply again, My explaination for 'why the mtime is so >> important' lost some informations and it is not clear enough, I will >> tell the details here: > > Let me see if I can summarize here. Basically: > > - You have a number of servers that have NFS mounts which hold large > repositories with packs in excess of 10 GB in size. > - You have a lot of clients that are fetching, and a smaller number of > clients that are pushing, some of which happen to freshen the mtimes > of the packs. > > ...and the mtimes being updated cause the disk cache to be invalidated? > > It's the last part that is so surprising to me. Ævar and I discussed > earlier in the thread that their understanding was that you had a backup > system which had to resynchronize an unchanged file because its metadata > had changed. > > But this is different than that. If I understand what you're saying > correctly, then you're saying that the disk caches themselves are > invalidated by changing the mtime. > > That is highly surprising to me, since the block cache should only be > invalidated if the *blocks* change, not metadata in the inode. It would > be good to confirm that this is actually what's happening. > > Thanks, > Taylor Oh, Maybe I didn't understand caching well enough, let me check it again, and thanks for your and Ævar's answers, they are really helpful.
