linux-kernel - Re: [RFC] high preempt off latency in vfree path

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Date:	Wed, 23 Mar 2016 12:03:49 -0700
From:	Joel Fernandes <joelaf@...126.com>
To:	Andi Kleen <ak@...ux.intel.com>
CC:	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	<tj@...nel.org>, <linux-rt-users@...r.kernel.org>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [RFC] high preempt off latency in vfree path

On 03/22/16 19:44, Andi Kleen wrote:
>> (1)
>> One is we reduce the number of lazy_max_pages (right now its around 32MB per core worth of pages).
>>
>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>> index aa3891e..2720f4f 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -564,7 +564,7 @@ static unsigned long lazy_max_pages(void)
>>
>>          log = fls(num_online_cpus());
>>
>> -       return log * (32UL * 1024 * 1024 / PAGE_SIZE);
>> +       return log * (8UL * 1024 * 1024 / PAGE_SIZE);
>>   }
>
> This seems like the right fix to me.  Perhaps even make it somewhat smaller.
>
> Even on larger systems it's probably fine because they have a lot more
> cores/threads these days, so it will be still sufficiently large.
>

Thanks Andi. I'll post a patch then.

Regards,
Joel

> -Andi
>