From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 13 Apr 2000 02:35:28 +0200 From: Jamie Lokier Subject: Re: Stack & policy Message-ID: <20000413023528.D27244@pcep-jamie.cern.ch> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: ; from James Antill on Wed, Apr 12, 2000 at 11:05:25AM -0400 Sender: owner-linux-mm@kvack.org Return-Path: To: James Antill Cc: axanth@tee.gr, linux-mm@kvack.org List-ID: James Antill wrote: > > Some time ago I posted a message about a kernel feature where the > > application can request the vma->vm_start of its stack virtual memory area > > in order to unmap part of the unused stack (esp - vma->vm_start). > > > > Such a feature is very useful for an alternative programming technique. > > Have you seen jamie and chuck talking about madvise() flags ? > Just doing madvise(cur_stack, MADV_DONTNEED, cur_stack - end_stack)[1] > after a function that uses alloca() or has a large auto should be > a pretty simple addition to gcc (although you might not want to put it > there). > > Those seem like a much better idea to me, as they can also be used in > pthreads (much as I hate pthreads) and other bits of memory that has > similar usage patterns. > This would also be much more likely to work on other OSes. You'd use MADV_FREE, as it allows the app to reuse stack pages immediately without the overhead of them being unmapped, remapped and rezeroed -- if it reuses them before the kernel finds another use for them. The most efficiently place to put this call is probably in a timer signal handler. You still need to get the base of the mapped region though. You can parse /proc/self/maps for this :-) -- Jamie -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux.eu.org/Linux-MM/