[0/2] smp: convert cpu_add_remove_lock int a rw lock

Message

Roger Pau Monne Feb. 13, 2020, 11:32 a.m. UTC

Hello,

The main aim of this series is to reduce the pressure around
cpu_add_remove_lock by converting it into a rw lock. Most users of the
lock want to take it in read mode, as they only care about the maps not
changing.

Patch #2 makes the writers take the lock in blocking mode, this is
mainly done to reduce the failure of the CPU plug/unplug operations,
since the lock is more contended now and trylock can easily fail if
there are readers.

Thanks, Roger.

Roger Pau Monne (2):
  smp: convert the cpu maps lock into a rw lock
  smp: convert cpu_hotplug_begin into a blocking lock acquisition

 xen/arch/x86/smpboot.c |  3 +--
 xen/common/cpu.c       | 29 ++++++++++++++++++-----------
 xen/include/xen/cpu.h  | 13 +++----------
 3 files changed, 22 insertions(+), 23 deletions(-)

Comments

Andrew Cooper Feb. 19, 2020, 12:22 p.m. UTC | #1

On 13/02/2020 11:32, Roger Pau Monne wrote:
> Hello,
>
> The main aim of this series is to reduce the pressure around
> cpu_add_remove_lock by converting it into a rw lock. Most users of the
> lock want to take it in read mode, as they only care about the maps not
> changing.
>
> Patch #2 makes the writers take the lock in blocking mode, this is
> mainly done to reduce the failure of the CPU plug/unplug operations,
> since the lock is more contended now and trylock can easily fail if
> there are readers.

Seems like a very sensible move.

Both patches Acked-by: Andrew Cooper <[e-mail]>