From mboxrd@z Thu Jan 1 00:00:00 1970 From: Minchan Kim Subject: Re: [PATCH v3 01/17] mm: support madvise(MADV_FREE) Date: Fri, 13 Nov 2015 15:15:11 +0900 Message-ID: <20151113061511.GB5235@bbox> References: <1447302793-5376-1-git-send-email-minchan@kernel.org> <1447302793-5376-2-git-send-email-minchan@kernel.org> <564421DA.9060809@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: In-Reply-To: <564421DA.9060809@gmail.com> Content-Disposition: inline Sender: owner-linux-mm@kvack.org To: Daniel Micay Cc: Andy Lutomirski , Andrew Morton , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Michael Kerrisk , Linux API , Hugh Dickins , Johannes Weiner , Rik van Riel , Mel Gorman , KOSAKI Motohiro , Jason Evans , "Kirill A. Shutemov" , Shaohua Li , Michal Hocko , yalin wang List-Id: linux-api@vger.kernel.org On Thu, Nov 12, 2015 at 12:21:30AM -0500, Daniel Micay wrote: > > I also think that the kernel should commit to either zeroing the page > > or leaving it unchanged in response to MADV_FREE (even if the decision > > of which to do is made later on). I think that your patch series does > > this, but only after a few of the patches are applied (the swap entry > > freeing), and I think that it should be a real guaranteed part of the > > semantics and maybe have a test case. > > This would be a good thing to test because it would be required to add > MADV_FREE_UNDO down the road. It would mean the same semantics as the > MEM_RESET and MEM_RESET_UNDO features on Windows, and there's probably > value in that for the sake of migrating existing software too. So, do you mean that we could implement MADV_FREE_UNDO with "read" opearation("just access bit marking) easily in future? If so, it would be good reason to change MADV_FREE from dirty bit to access bit. Okay, I will look at that. > > For one example, it could be dropped into Firefox: > > https://dxr.mozilla.org/mozilla-central/source/memory/volatile/VolatileBufferWindows.cpp > > And in Chromium: > > https://code.google.com/p/chromium/codesearch#chromium/src/base/memory/discardable_shared_memory.cc > > Worth noting that both also support the API for pinning/unpinning that's > used by Android's ashmem too. Linux really needs a feature like this for > caches. Firefox simply doesn't drop the memory at all on Linux right now: > > https://dxr.mozilla.org/mozilla-central/source/memory/volatile/VolatileBufferFallback.cpp > > (Lock == pin, Unlock == unpin) > > For reference: > > https://msdn.microsoft.com/en-us/library/windows/desktop/aa366887(v=vs.85).aspx > -- 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