LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Christopher Lameter <cl@linux.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Mikulas Patocka <mpatocka@redhat.com>,
	Mike Snitzer <snitzer@redhat.com>,
	Matthew Wilcox <willy@infradead.org>,
	Pekka Enberg <penberg@kernel.org>,
	linux-mm@kvack.org, dm-devel@redhat.com,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND] slab: introduce the flag SLAB_MINIMIZE_WASTE
Date: Tue, 17 Apr 2018 11:38:02 -0500 (CDT)	[thread overview]
Message-ID: <alpine.DEB.2.20.1804171135190.18801@nuc-kabylake> (raw)
In-Reply-To: <f8f736fe-9e0e-acd2-8040-f4f25ea5a7a2@suse.cz>

On Tue, 17 Apr 2018, Vlastimil Babka wrote:

> On 04/17/2018 04:45 PM, Christopher Lameter wrote:

> > But then higher order allocs are generally seen as problematic.
>
> I think in this case they are better than wasting/fragmenting 384kB for
> 640kB object.

Well typically we have suggested that people use vmalloc in the past.


> > Note that SLUB will fall back to smallest order already if a failure
> > occurs so increasing slub_max_order may not be that much of an issue.
> >
> > Maybe drop the max order limit completely and use MAX_ORDER instead?
>
> For packing, sure. For performance, please no (i.e. don't try to
> allocate MAX_ORDER for each and every cache).

No of course not. We would have to modify the order selection on kmem
cache creation.

> > That
> > means that callers need to be able to tolerate failures.
>
> Is it any different from now? I suppose there would still be
> smallest-order fallback involved in sl*b itself? And if your allocation
> is so large it can fail even with the fallback (i.e. >= costly order),
> you need to tolerate failures anyway?

Failures can occur even with < costly order as far as I can telkl. Order 0
is the only safe one.

> One corner case I see is if there is anyone who would rather use their
> own fallback instead of the space-wasting smallest-order fallback.
> Maybe we could map some GFP flag to indicate that.

Well if you have a fallback then maybe the slab allocator should not fall
back on its own but let the caller deal with it.

  reply	other threads:[~2018-04-17 16:38 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <alpine.LRH.2.02.1803201740280.21066@file01.intranet.prod.int.rdu2.redhat.com>
     [not found] ` <alpine.DEB.2.20.1803211024220.2175@nuc-kabylake>
     [not found]   ` <alpine.LRH.2.02.1803211153320.16017@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]     ` <alpine.DEB.2.20.1803211226350.3174@nuc-kabylake>
     [not found]       ` <alpine.LRH.2.02.1803211425330.26409@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]         ` <20c58a03-90a8-7e75-5fc7-856facfb6c8a@suse.cz>
     [not found]           ` <20180413151019.GA5660@redhat.com>
     [not found]             ` <ee8807ff-d650-0064-70bf-e1d77fa61f5c@suse.cz>
     [not found]               ` <20180416142703.GA22422@redhat.com>
     [not found]                 ` <alpine.LRH.2.02.1804161031300.24222@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]                   ` <20180416144638.GA22484@redhat.com>
2018-04-16 19:32                     ` Mikulas Patocka
2018-04-17 14:45                       ` Christopher Lameter
2018-04-17 16:16                         ` Vlastimil Babka
2018-04-17 16:38                           ` Christopher Lameter [this message]
2018-04-17 19:09                             ` Mikulas Patocka
2018-04-17 17:26                           ` Mikulas Patocka
2018-04-17 19:13                             ` Vlastimil Babka
2018-04-17 19:06                         ` Mikulas Patocka
2018-04-18 14:55                           ` Christopher Lameter
2018-04-25 21:04                             ` Mikulas Patocka
2018-04-25 23:24                               ` Mikulas Patocka
2018-04-26 19:01                                 ` Christopher Lameter
2018-04-26 21:09                                   ` Mikulas Patocka
2018-04-27 16:41                                     ` Christopher Lameter
2018-04-27 19:19                                       ` Mikulas Patocka
2018-06-13 17:01                                         ` Mikulas Patocka
2018-06-13 18:16                                           ` Christoph Hellwig
2018-06-13 18:53                                             ` Mikulas Patocka
2018-04-26 18:51                               ` Christopher Lameter
     [not found]                     ` <alpine.LRH.2.02.1804161054410.17807@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]                       ` <alpine.DEB.2.20.1804161018030.9397@nuc-kabylake>
     [not found]                         ` <alpine.LRH.2.02.1804161123400.17807@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]                           ` <alpine.DEB.2.20.1804161043430.9622@nuc-kabylake>
     [not found]                             ` <alpine.LRH.2.02.1804161532480.19492@file01.intranet.prod.int.rdu2.redhat.com>
     [not found]                               ` <b0e6ccf6-06ce-e50b-840e-c8d3072382fd@suse.cz>
2018-04-16 21:01                                 ` Mikulas Patocka
2018-04-17 14:40                                   ` Christopher Lameter
2018-04-17 18:53                                     ` Mikulas Patocka
2018-04-17 21:42                                       ` Christopher Lameter

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=alpine.DEB.2.20.1804171135190.18801@nuc-kabylake \
    --to=cl@linux.com \
    --cc=akpm@linux-foundation.org \
    --cc=dm-devel@redhat.com \
    --cc=iamjoonsoo.kim@lge.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mpatocka@redhat.com \
    --cc=penberg@kernel.org \
    --cc=rientjes@google.com \
    --cc=snitzer@redhat.com \
    --cc=vbabka@suse.cz \
    --cc=willy@infradead.org \
    --subject='Re: [PATCH RESEND] slab: introduce the flag SLAB_MINIMIZE_WASTE' \
    /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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).