From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <41C40D3E.9050507@yahoo.com.au> Date: Sat, 18 Dec 2004 21:58:06 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [PATCH 4/10] alternate 4-level page tables patches References: <41C3D453.4040208@yahoo.com.au> <41C3D479.40708@yahoo.com.au> <41C3D48F.8080006@yahoo.com.au> <41C3D4AE.7010502@yahoo.com.au> <41C3D4C8.1000508@yahoo.com.au> <20041218104522.GI771@holomorphy.com> In-Reply-To: <20041218104522.GI771@holomorphy.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: William Lee Irwin III Cc: Linux Memory Management , Andi Kleen , Hugh Dickins , Linus Torvalds , Andrew Morton List-ID: William Lee Irwin III wrote: > On Sat, Dec 18, 2004 at 05:57:12PM +1100, Nick Piggin wrote: > >>Rename clear_page_tables to clear_page_range. clear_page_range takes byte >>ranges, and aggressively frees page table pages. Maybe useful to control >>page table memory consumption on 4-level architectures (and even 3 level >>ones). >>Possible downsides are: >>- flush_tlb_pgtables gets called more often (only a problem for sparc64 >> AFAIKS). >>- the opportunistic "expand to fill PGDIR_SIZE hole" logic that ensures >> something actually gets done under the old system is still in place. >> This could sometimes make unmapping small regions more inefficient. There >> are some other solutions to look at if this is the case though. >>Signed-off-by: Nick Piggin > > > I wrote something equivalent to this in September, but dropped it on the > floor after some private replies etc. indicated no one gave a damn about > the testcase I posted in Message-ID: <20040908110718.GX3106@holomorphy.com> > where the pagetable leak fooled the OOM killer into shooting the wrong > processes long enough to trigger a panic() in oom_kill.c > > Hmm... I actually didn't see your post, but it seems like something worth pursuing. My incling is that the hybrid expand-to-hole / refcounting approach I outlined earlier in the thread might be the way to go. I'll be interested to hear what the powers that be think. -- 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: aart@kvack.org