From: Malcolm Crossley <malcolm.crossley@citrix.com>
To: JBeulich@suse.com, andrew.cooper3@citrix.com,
Marcos.Matsunaga@oracle.com, keir@xen.org,
konrad.wilk@oracle.com, george.dunlap@eu.citrix.com
Cc: xen-devel@lists.xenproject.org, dario.faggioli@citrix.com,
stefano.stabellini@citrix.com,
Malcolm Crossley <malcolm.crossley@citrix.com>
Subject: [PATCHv6 0/3] Implement per-cpu reader-writer locks
Date: Fri, 22 Jan 2016 13:41:44 +0000 [thread overview]
Message-ID: <1453470107-27861-1-git-send-email-malcolm.crossley@citrix.com> (raw)
This patch series adds per-cpu reader-writer locks as a generic lock
implementation and then converts the grant table and p2m rwlocks to
use the percpu rwlocks, in order to improve multi-socket host performance.
CPU profiling has revealed the rwlocks themselves suffer from severe cache
line bouncing due to the cmpxchg operation used even when taking a read lock.
Multiqueue paravirtualised I/O results in heavy contention of the grant table
and p2m read locks of a specific domain and so I/O throughput is bottlenecked
by the overhead of the cache line bouncing itself.
Per-cpu read locks avoid lock cache line bouncing by using a per-cpu data
area to record a CPU has taken the read lock. Correctness is enforced for the
write lock by using a per lock barrier which forces the per-cpu read lock
to revert to using a standard read lock. The write lock then polls all
the percpu data area until active readers for the lock have exited.
Removing the cache line bouncing on a multi-socket Haswell-EP system
dramatically improves performance, with 16 vCPU network IO performance going
from 15 gb/s to 64 gb/s! The host under test was fully utilising all 40
logical CPU's at 64 gb/s, so a bigger logical CPU host may see an even better
IO improvement.
Note: Benchmarking of the these performance improvements should be done with
the non debug version of the hypervisor otherwise the map_domain_page spinlock
is the main bottleneck.
Changes in V6:
- Fix compilation on ARM
Changes in V5:
- Move percpu_owner ASSERTS to be inline function
- Rename grant table rwlock wrappers
Changes in V4:
- Fix the ASSERTS for the percpu_owner check
Changes in V3:
- Add percpu rwlock owner for debug Xen builds
- Validate percpu rwlock owner at runtime for debug Xen builds
- Fix hard tab issues
- Use percpu rwlock wrappers for grant table rwlock users
- Add comments why rw_is_locked ASSERTS have been removed in grant table code
Changes in V2:
- Add Cover letter
- Convert p2m rwlock to percpu rwlock
- Improve percpu rwlock to safely handle simultaneously holding 2 or more
locks
- Move percpu rwlock barrier from global to per lock
- Move write lock cpumask variable to a percpu variable
- Add macros to help initialise and use percpu rwlocks
- Updated IO benchmark results to cover revised locking implementation
Malcolm Crossley (3):
rwlock: Add per-cpu reader-writer lock infrastructure
grant_table: convert grant table rwlock to percpu rwlock
p2m: convert p2m rwlock to percpu rwlock
xen/arch/arm/mm.c | 4 +-
xen/arch/x86/mm.c | 4 +-
xen/arch/x86/mm/mm-locks.h | 12 ++--
xen/arch/x86/mm/p2m.c | 1 +
xen/common/grant_table.c | 124 +++++++++++++++++++++++-------------------
xen/common/spinlock.c | 45 +++++++++++++++
xen/include/asm-arm/percpu.h | 5 ++
xen/include/asm-x86/mm.h | 2 +-
xen/include/asm-x86/percpu.h | 6 ++
xen/include/xen/grant_table.h | 24 +++++++-
xen/include/xen/percpu.h | 4 ++
xen/include/xen/spinlock.h | 116 +++++++++++++++++++++++++++++++++++++++
12 files changed, 281 insertions(+), 66 deletions(-)
--
1.7.12.4
next reply other threads:[~2016-01-22 13:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-22 13:41 Malcolm Crossley [this message]
2016-01-22 13:41 ` [PATCHv6 1/3] rwlock: Add per-cpu reader-writer lock infrastructure Malcolm Crossley
2016-01-22 13:54 ` Ian Campbell
2016-01-22 14:16 ` Malcolm Crossley
2016-01-22 14:22 ` Ian Campbell
2016-01-22 14:30 ` Malcolm Crossley
2016-01-22 14:45 ` Ian Campbell
2016-01-22 14:25 ` Ross Lagerwall
2016-01-22 13:41 ` [PATCHv6 2/3] grant_table: convert grant table rwlock to percpu rwlock Malcolm Crossley
2016-01-22 15:15 ` Jan Beulich
2016-01-22 15:22 ` Ian Campbell
2016-01-22 15:34 ` Jan Beulich
2016-01-22 15:53 ` Ian Campbell
2016-01-22 13:41 ` [PATCHv6 3/3] p2m: convert p2m " Malcolm Crossley
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1453470107-27861-1-git-send-email-malcolm.crossley@citrix.com \
--to=malcolm.crossley@citrix.com \
--cc=JBeulich@suse.com \
--cc=Marcos.Matsunaga@oracle.com \
--cc=andrew.cooper3@citrix.com \
--cc=dario.faggioli@citrix.com \
--cc=george.dunlap@eu.citrix.com \
--cc=keir@xen.org \
--cc=konrad.wilk@oracle.com \
--cc=stefano.stabellini@citrix.com \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.