On Fri, Mar 08, 2024 at 05:00:58PM +0100, Jan Kara wrote: > On Wed 06-03-24 16:51:06, Amir Goldstein wrote: > > On Thu, Feb 15, 2024 at 10:36 AM Jan Kara <jack@xxxxxxx> wrote: > > > On Wed 14-02-24 15:40:31, Amir Goldstein wrote: > > > > > > > > Merged your improvement now (and I've split off the cleanup into a separate > > > > > > > > change and dropped the creation of fsnotify_path() which seemed a bit > > > > > > > > pointless with a single caller). All pushed out. > > > > > > > > > > > > > > > > > > > > > > > > > > > Jan & Jens, > > > > > > > > > > > > Although Jan has already queued this v3 patch with sufficient performance > > > > > > improvement for Jens' workloads, I got a performance regression report from > > > > > > kernel robot on will-it-scale microbenchmark (buffered write loop) > > > > > > on my fan_pre_content patches, so I tried to improve on the existing solution. > > > > > > > > > > > > I tried something similar to v1/v2 patches, where the sb keeps accounting > > > > > > of the number of watchers for specific sub-classes of events. > > > > > > > > > > > > I've made two major changes: > > > > > > 1. moved to counters into a per-sb state object fsnotify_sb_connector > > > > > > as Christian requested > > > > > > 2. The counters are by fanotify classes, not by specific events, so they > > > > > > can be used to answer the questions: > > > > > > a) Are there any fsnotify watchers on this sb? > > > > > > b) Are there any fanotify permission class listeners on this sb? > > > > > > c) Are there any fanotify pre-content (a.k.a HSM) class listeners on this sb? > > > > > > > > > > > > I think that those questions are very relevant in the real world, because > > > > > > a positive answer to (b) and (c) is quite rare in the real world, so the > > > > > > overhead on the permission hooks could be completely eliminated in > > > > > > the common case. > > > > > > > > > > > > If needed, we can further bisect the class counters per specific painful > > > > > > events (e.g. FAN_ACCESS*), but there is no need to do that before > > > > > > we see concrete benchmark results. > > > ... > > > > > > > > Then I dislike how we have to specialcase superblock in quite a few places > > > > > and add these wrappers and what not. This seems to be mostly caused by the > > > > > fact that you directly embed fsnotify_mark_connector into fsnotify_sb_info. > > > > > What if we just put fsnotify_connp_t there? I understand that this will > > > > > mean one more pointer fetch if there are actually marks attached to the > > > > > superblock and the event mask matches s_fsnotify_mask. But in that case we > > > > > are likely to generate the event anyway so the cost of that compared to > > > > > event generation is negligible? > > > > > > > > > > > > > I guess that can work. > > > > I can try it and see if there are any other complications. > > > > > > > > > And I'd allocate fsnotify_sb_info on demand from fsnotify_add_mark_locked() > > > > > which means that we need to pass object pointer (in the form of void *) > > > > > instead of fsnotify_connp_t to various mark adding functions (and transform > > > > > it to fsnotify_connp_t only in fsnotify_add_mark_locked() after possibly > > > > > setting up fsnotify_sb_info). Passing void * around is not great but it > > > > > should be fairly limited (and actually reduces the knowledge of fsnotify > > > > > internals outside of the fsnotify core). > > > > > > > > Unless I am missing something, I think we only need to pass an extra sb > > > > arg to fsnotify_add_mark_locked()? and it does not sound like a big deal. > > > > For adding an sb mark, connp arg could be NULL, and then we get connp > > > > from sb->fsnotify_sb_info after making sure that it is allocated. > > > > > > Yes that would be another possibility but frankly I like passing the > > > 'object' pointer instead of connp pointer a bit more. But we can see how > > > the code looks like. > > > > Ok, here it is: > > > > https://github.com/amir73il/linux/commits/fsnotify-sbinfo/ > > > > I agree that the interface does end up looking better this way. > > Yep, the interface looks fine. I have left some comments on github > regarding typos and some suspicious things. > > > I've requested to re-test performance on fsnotify-sbinfo. > > > > You can use this rebased branch to look at the diff from the > > the previous patches that were tested by 0day: > > > > https://github.com/amir73il/linux/commits/fsnotify-sbconn/ > > > > If you have the bandwidth to consider those patches as candidates > > for (the second half of?) 6.9 merge window, I can post them for review. > > Well, unless Linus does rc8, I don't think we should queue these for the > merge window as it is too late by now. But please post them for review, > I'll have a look. I can then push them to my tree early into a stable > branch and you can base your patches on my branch. If the patches then need > to go through VFS tree, Christian is fine with pulling my tree... I'm absolutely opposed to touching anything that you do. I'm joking of course, I'm very happy to pull from you!
