linux-kernel - [PATCH -next 0/2] fs/epoll: loosen irq safety when possible

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Date:   Fri, 20 Jul 2018 10:29:54 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     akpm@...ux-foundation.org
Cc:     jbaron@...mai.com, viro@...iv.linux.org.uk,
        linux-kernel@...r.kernel.org, dave@...olabs.net
Subject: [PATCH -next 0/2] fs/epoll: loosen irq safety when possible

Hi,

Both patches replace saving+restoring interrupts when taking the
ep->lock (now the waitqueue lock), with just disabling local irqs.
This shows immediate performance benefits in patch 1 for an epoll
workload running on Xen. The main concern we need to have with this
sort of changes in epoll is the ep_poll_callback() which is passed
to the wait queue wakeup and is done very often under irq context,
this patch does not touch this call.

Patches have been tested pretty heavily with the customer workload,
microbenchmarks, ltp testcases and two high level workloads that
use epoll under the hood: nginx and libevent benchmarks.

Details are in the individual patches.

Applies on top of mmotd.

Thanks!

Davidlohr Bueso (2):
  fs/epoll: loosen irq safety in ep_scan_ready_list()
  fs/epoll: loosen irq safety in epoll_insert() and epoll_remove()

 fs/eventpoll.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

-- 
2.16.4