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Date: Tue, 26 Feb 2019 16:06:01 +0300
From: Vladimir Davydov <vdavydov.dev@gmail.com>
Subject: Re: [RFC v3] fiber: Increase default stack size
Message-ID: <20190226130601.o33yi7gkihayep5m@esperanza>
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To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: =?utf-8?B?0JPQtdC+0YDQs9C40Lkg0JrQuNGA0LjRh9C10L3QutC+?= <georgy@tarantool.org>, tarantool-patches@freelists.org
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On Tue, Feb 26, 2019 at 03:54:57PM +0300, Cyrill Gorcunov wrote:
> On Tue, Feb 26, 2019 at 03:34:56PM +0300, Vladimir Davydov wrote:
> > > 
> > > If we want to scatter we should simply put marks at page bounds.
> > > Dirtifying somewhere inside middle of a page is useless.
> > 
> > Hmm, why? Consider the example with PATH_MAX buffer. Putting dirty marks
> > at page boundaries doesn't guarantee any of them will get overwritten by
> > the buffer if only a few hundred of bytes are used. I think we should
> > dirty the last page or two at random intervals - this should increase
> > the chance that at least one mark is overwritten by any function that is
> > eager for the stack.
> 
> Ah, I got what you mean. Look, maybe we should consider pagemap too?
> iirc readin pagemap should be cheap but need to read the code though,
> will try once time permit.

We are paranoid about any syscalls so no, I don't think you'll be able
to sell it. I think we'd better stick to poisoning.