All of lore.kernel.org
 help / color / mirror / Atom feed
From: Andrew Morton <akpm@linux-foundation.org>
To: paulmck@kernel.org
Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com,
	iamjoonsoo.kim@lge.com, hannes@cmpxchg.org, willy@infradead.org,
	urezki@gmail.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: Raw spinlocks and memory allocation
Date: Fri, 31 Jul 2020 13:38:34 -0700	[thread overview]
Message-ID: <20200731133834.517fdfee99b7ed2239f576aa@linux-foundation.org> (raw)
In-Reply-To: <20200730231205.GA11265@paulmck-ThinkPad-P72>

On Thu, 30 Jul 2020 16:12:05 -0700 "Paul E. McKenney" <paulmck@kernel.org> wrote:

> So, may we add a GFP_ flag that will cause kmalloc() and friends to return
> NULL when they would otherwise need to acquire their non-raw spinlock?
> This avoids adding any overhead to the slab-allocator fastpaths, but
> allows callback invocation to reduce cache misses without having to
> restructure some existing callers of call_rcu() and potential future
> callers of kfree_rcu().

We have eight free gfp_t bits so that isn't a problem.

Adding a test-n-branch to the kmalloc() fastpath may well be a concern.

Which of mm/sl?b.c are affected?

A doesnt-need-to-really-work protopatch would help us understand the
potential cost?

  reply	other threads:[~2020-07-31 20:38 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 23:12 Raw spinlocks and memory allocation Paul E. McKenney
2020-07-31 20:38 ` Andrew Morton [this message]
2020-07-31 20:48   ` Paul E. McKenney
2020-07-31 20:59     ` Matthew Wilcox
2020-07-31 21:24       ` Paul E. McKenney
2020-07-31 21:29         ` Andrew Morton
2020-07-31 22:30           ` Paul E. McKenney
2020-07-31 22:47             ` Matthew Wilcox
2020-08-01  0:02               ` Paul E. McKenney

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=20200731133834.517fdfee99b7ed2239f576aa@linux-foundation.org \
    --to=akpm@linux-foundation.org \
    --cc=cl@linux.com \
    --cc=hannes@cmpxchg.org \
    --cc=iamjoonsoo.kim@lge.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=paulmck@kernel.org \
    --cc=penberg@kernel.org \
    --cc=rientjes@google.com \
    --cc=urezki@gmail.com \
    --cc=willy@infradead.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.