On Wed, 2022-08-17 at 15:48 -0500, Benjamin Marzinski wrote: > When there are a huge number of paths (> 10000) The amount of time > that > the checkerloop can hold the vecs lock for while checking the paths > can > get to be large enough that it starves other vecs lock users. If > path > checking takes long enough, it's possible that uxlsnr threads will > never > run. To deal with this, this patchset makes it possible to drop the > vecs > lock while checking the paths, and then reacquire it and continue > with > the next path to check. > > My choice of only checking if there are waiters every 128 paths > checked > and only interrupting if path checking has taken more than a second > are > arbitrary. I didn't want to slow down path checking in the common > case > where this isn't an issue, and I wanted to avoid path checking > getting > starved by other vecs->lock users. Having the checkerloop wait for > 10000 > nsec was based on my own testing with a setup using 4K multipath > devies > with 4 paths each. This was almost always long enough for the uevent > or > uxlsnr client to grab the vecs lock, but I'm not sure how dependent > this > is on details of the system. For instance with my setup in never took > more than 20 seconds to check the paths. and usually, a looping > through > all the paths took well under 10 seconds, most often under 5. I would > only occasionally run into situations where a uxlsnr client would > time > out. > > V2 Changes: > 0003: Switched to a simpler method of determining the path to > continue > checking at, as suggested by Martin Wilck. Also fixed a bug > when > the previous index was larger than the current vector size. > > Benjamin Marzinski (6): > multipathd: Use regular pthread_mutex_t for waiter_lock > multipathd: track waiters for mutex_lock > multipathd: Occasionally allow waiters to interrupt checking paths > multipathd: allow uxlsnr clients to interrupt checking paths > multipathd: fix uxlsnr timeout > multipathd: Don't check if timespec.tv_sec is zero For the series: Reviewed-by: Martin Wilck <mwilck@xxxxxxxx> > > libmultipath/lock.h | 16 +++++ > libmultipath/structs.h | 1 + > multipathd/main.c | 147 ++++++++++++++++++++++++++------------- > -- > multipathd/uxlsnr.c | 23 +++++-- > multipathd/uxlsnr.h | 1 + > multipathd/waiter.c | 14 ++-- > 6 files changed, 136 insertions(+), 66 deletions(-) > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
