From: Greg Kroah-Hartman <firstname.lastname@example.org> To: Minchan Kim <email@example.com> Cc: Tejun Heo <firstname.lastname@example.org>, LKML <email@example.com> Subject: Re: [RFC PATCH] kernfs: release kernfs_mutex before the inode allocation Date: Tue, 16 Nov 2021 20:49:46 +0100 [thread overview] Message-ID: <YZQLWq7WMSRF2xCM@kroah.com> (raw) In-Reply-To: <firstname.lastname@example.org> On Tue, Nov 16, 2021 at 11:43:17AM -0800, Minchan Kim wrote: > The kernfs implementation has big lock granularity(kernfs_rwsem) so > every kernfs-based(e.g., sysfs, cgroup, dmabuf) fs are able to compete > the lock. Thus, if one of userspace goes the sleep under holding > the lock for a long time, rest of them should wait it. A example is > the holder goes direct reclaim with the lock since it needs memory > allocation. Let's fix it at common technique that release the lock > and then allocate the memory. Fortunately, kernfs looks like have > an refcount so I hope it's fine. > > Signed-off-by: Minchan Kim <email@example.com> > --- > fs/kernfs/dir.c | 14 +++++++++++--- > fs/kernfs/inode.c | 2 +- > fs/kernfs/kernfs-internal.h | 1 + > 3 files changed, 13 insertions(+), 4 deletions(-) What workload hits this lock to cause it to be noticable? There was a bunch of recent work in this area to make this much more fine-grained, and the theoritical benchmarks that people created (adding 10s of thousands of scsi disks at boot time) have gotten better. But in that work, no one could find a real benchmark or use case that anyone could even notice this type of thing. What do you have that shows this? thanks, greg k-h
next prev parent reply other threads:[~2021-11-16 19:49 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-11-16 19:43 Minchan Kim 2021-11-16 19:49 ` Greg Kroah-Hartman [this message] 2021-11-16 21:36 ` Minchan Kim 2021-11-17 6:44 ` Greg Kroah-Hartman 2021-11-17 7:27 ` Minchan Kim 2021-11-17 7:39 ` Greg Kroah-Hartman 2021-11-17 21:43 ` Minchan Kim 2021-11-17 21:45 ` Tejun Heo 2021-11-17 22:13 ` Minchan Kim 2021-11-17 22:23 ` Tejun Heo 2021-11-18 1:55 ` Minchan Kim 2021-11-18 16:35 ` Tejun Heo
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