5d0ce3595a
Patch series "/msg: mitigate the lock contention in ipc/msg", v6. Here are two patches to mitigate the lock contention in ipc/msg. The 1st patch is to add the new interface percpu_counter_add_local and percpu_counter_sub_local. The batch size in percpu_counter_add_batch should be very large in heavy writing and rare reading case. Add the "_local" version, and mostly it will do local adding, reduce the global updating and mitigate lock contention in writing. The 2nd patch is to use percpu_counter instead of atomic update in ipc/msg. The msg_bytes and msg_hdrs atomic counters are frequently updated when IPC msg queue is in heavy use, causing heavy cache bounce and overhead. Change them to percpu_counter greatly improve the performance. Since there is one percpu struct per namespace, additional memory cost is minimal. Reading of the count done in msgctl call, which is infrequent. So the need to sum up the counts in each CPU is infrequent. This patch (of 2): The batch size in percpu_counter_add_batch should be very large in heavy writing and rare reading case. Add the "_local" version, and mostly it will do local adding, reduce the global updating and mitigate lock contention in writing. Link: https://lkml.kernel.org/r/20220913192538.3023708-1-jiebin.sun@intel.com Link: https://lkml.kernel.org/r/20220913192538.3023708-2-jiebin.sun@intel.com Signed-off-by: Jiebin Sun <jiebin.sun@intel.com> Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com> Cc: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com> Cc: Alexey Gladkov <legion@kernel.org> Cc: Christoph Lameter <cl@linux.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Shakeel Butt <shakeelb@google.com> Cc: Tejun Heo <tj@kernel.org> Cc: Vasily Averin <vasily.averin@linux.dev> Cc: Davidlohr Bueso <dave@stgolabs.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.