linux-kernel - Re: [PATCH 07/15] mm: Add ___GFP

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Message-ID: <CAMEtUuwvJZZ2UpMGm+=BJ88W87EOb-Rof4Ai3ya+Mto5_K8Thg@mail.gmail.com>
Date:	Mon, 2 Mar 2015 11:29:35 -0800
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/15] mm: Add ___GFP_NOTRACE

On Mon, Mar 2, 2015 at 10:54 AM, Tom Zanussi
<tom.zanussi@...ux.intel.com> wrote:
>> >
>> > The idea would be that instead of getting your individually kmalloc'ed
>> > elements on-demand from kmalloc while in the handler, you'd get them
>> > from a pool you've pre-allocated when you set up the table.  This could
>> > be from a list of individual entries you've already kmalloc'ed ahead of
>> > time, or from an array of n * sizeof(entry).
>>
>> would work, but kinda ugly, since we will pre-allocate a lot
>> and may not be using it at all.
>>
>
> That's true but you have a user-defined map limit anyway, which you can
> adjust to minimize wastage.  And allocating ahead of time also means you
> perturb the system less while actually tracing.

nope. it's the other way around.
using kmalloc is faster and less overhead on the whole system
then grabbing cache-cold objects from special pool.
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