Messages in this thread | | | Date | Mon, 19 Nov 2018 11:02:48 +0100 | From | Cornelia Huck <> | Subject | Re: [PATCH v2] vfio/pci: Parallelize device open and release |
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On Fri, 16 Nov 2018 09:18:41 -0700 Alex Williamson <alex.williamson@redhat.com> wrote:
> In commit 61d792562b53 ("vfio-pci: Use mutex around open, release, and > remove") a mutex was added to freeze the refcnt for a device so that > we can handle errors and perform bus resets on final close. However, > bus resets can be rather slow and a global mutex here is undesirable. > Evaluating the potential locking granularity, a per-device mutex > provides the best resolution but with multiple devices on a bus all > released concurrently, they'll race to acquire each other's mutex, > likely resulting in no reset at all if we use trylock. We therefore > lock at the granularity of the bus/slot reset as we're only attempting > a single reset for this group of devices anyway. This allows much > greater scaling as we're bounded in the number of devices protected by > a single reflck object. > > Reported-by: Christian Ehrhardt <christian.ehrhardt@canonical.com> > Tested-by: Christian Ehrhardt <christian.ehrhardt@canonical.com> > Reviewed-by: Eric Auger <eric.auger@redhat.com> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com> > --- > > v2: > - Rolled in PTR_ERR_OR_ZERO suggestion from kbuild bot > - Updated commit log and comments per Eric's feedback > > drivers/vfio/pci/vfio_pci.c | 160 ++++++++++++++++++++++++++++++----- > drivers/vfio/pci/vfio_pci_private.h | 6 + > 2 files changed, 142 insertions(+), 24 deletions(-)
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
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