From: Vlastimil Babka <vbabka@suse.cz>
To: Eric Dumazet <edumazet@google.com>, Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: __GFP_REPEAT usage in fq_alloc_node
Date: Fri, 6 Jan 2017 17:31:40 +0100 [thread overview]
Message-ID: <20901069-5eb7-f5ff-0641-078635544531@suse.cz> (raw)
In-Reply-To: <CANn89i+QZs0cSPK21qMe6LXw+AeAMZ_tKEDUEnCsJ_cd+q0t-g@mail.gmail.com>
On 01/06/2017 04:39 PM, Eric Dumazet wrote:
> On Fri, Jan 6, 2017 at 7:20 AM, Michal Hocko <mhocko@kernel.org> wrote:
>>
>> Hi Eric,
>> I am currently checking kmalloc with vmalloc fallback users and convert
>> them to a new kvmalloc helper [1]. While I am adding a support for
>> __GFP_REPEAT to kvmalloc [2] I was wondering what is the reason to use
>> __GFP_REPEAT in fq_alloc_node in the first place. c3bd85495aef
>> ("pkt_sched: fq: more robust memory allocation") doesn't mention
>> anything. Could you clarify this please?
>>
>> Thanks!
>
> I guess this question applies to all __GFP_REPEAT usages in net/ ?
>
> At the time, tests on the hardware I had in my labs showed that
> vmalloc() could deliver pages spread
> all over the memory and that was a small penalty (once memory is
> fragmented enough, not at boot time)
I wonder what's that cause of the penalty (when accessing the vmapped
area I suppose?) Is it higher risk of collisions cache misses within the
area, compared to consecutive physical adresses?
> I guess this wont be anymore a concern if I can finish my pending work
> about vmalloc() trying to get adjacent pages
> https://lkml.org/lkml/2016/12/21/285
>
> Thanks.
>
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next prev parent reply other threads:[~2017-01-06 16:31 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-06 15:20 Michal Hocko
2017-01-06 15:37 ` Eric Dumazet
2017-01-06 15:39 ` Eric Dumazet
2017-01-06 16:07 ` Michal Hocko
2017-01-06 16:19 ` Michal Hocko
2017-01-07 3:33 ` [PATCH] net: use kvmalloc rather than open coded variant kbuild test robot
2017-01-07 9:19 ` Michal Hocko
2017-01-07 3:35 ` kbuild test robot
2017-01-09 10:22 ` __GFP_REPEAT usage in fq_alloc_node Michal Hocko
2017-01-09 16:00 ` Eric Dumazet
2017-01-09 17:45 ` Michal Hocko
2017-01-09 17:53 ` Eric Dumazet
2017-01-14 23:43 ` [PATCH] net_sched: use kvmalloc rather than opencoded variant kbuild test robot
2017-01-16 8:54 ` Michal Hocko
2017-01-06 16:31 ` Vlastimil Babka [this message]
2017-01-06 16:48 ` __GFP_REPEAT usage in fq_alloc_node Eric Dumazet
2017-01-06 16:50 ` Eric Dumazet
2017-01-06 16:55 ` Vlastimil Babka
2017-01-06 17:08 ` Eric Dumazet
2017-01-06 17:18 ` Vlastimil Babka
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