From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 16 Jan 2006 14:06:49 +0100 From: Andrea Arcangeli Subject: differences between MADV_FREE and MADV_DONTNEED Message-ID: <20060116130649.GE15897@opteron.random> References: <20051029025119.GA14998@ccure.user-mode-linux.org> <1130788176.24503.19.camel@localhost.localdomain> <20051101000509.GA11847@ccure.user-mode-linux.org> <1130894101.24503.64.camel@localhost.localdomain> <20051102014321.GG24051@opteron.random> <1130947957.24503.70.camel@localhost.localdomain> <20051111162511.57ee1af3.akpm@osdl.org> <1131755660.25354.81.camel@localhost.localdomain> <20051111174309.5d544de4.akpm@osdl.org> <43757263.2030401@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43757263.2030401@us.ibm.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Badari Pulavarty Cc: Andrew Morton , linux-kernel@vger.kernel.org, hugh@veritas.com, dvhltc@us.ibm.com, linux-mm@kvack.org, blaisorblade@yahoo.it, jdike@addtoit.com List-ID: Now that MADV_REMOVE is in, should we discuss MADV_FREE? MADV_FREE in Solaris is destructive and only works on anonymous memory, while MADV_DONTNEED seems to never be destructive (which I assume it means it's a noop on anonymous memory). Our MADV_DONTNEED is destructive on anonymous memory, while it's non-destructive on file mappings. Perhaps we could move the destructive anonymous part of MADV_DONTNEED to MADV_FREE? Or we could as well go relaxed and define MADV_FREE and MADV_DONTNEED the same way (that still leaves the question if we risk to break apps ported from solaris where MADV_DONTNEED is apparently always not destructive). I only read the docs, I don't know in practice what MADV_DONTNEED does on solaris (does it return -EINVAL if run on anonymous memory or not?). http://docs.sun.com/app/docs/doc/816-5168/6mbb3hrgk?a=view BTW, I don't know how other specifications define MADV_FREE, but besides MADV_REMOVE I've also got the request to provide MADV_FREE in linux, this is why I'm asking. (right now I'm telling them to use #ifdef __linux__ #define MADV_FREE MADV_DONTNEED but that's quite an hack since it could break if we make MADV_DONTNEED non-destructive in the future) Thanks. -- 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-mm.org/ . Don't email: email@kvack.org