From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [patch 2/2] htlb forget rss with pt sharing From: Peter Zijlstra In-Reply-To: <000101c6f3b2$7f9cf980$ff0da8c0@amr.corp.intel.com> References: <000101c6f3b2$7f9cf980$ff0da8c0@amr.corp.intel.com> Content-Type: text/plain Date: Sat, 21 Oct 2006 17:58:41 +0200 Message-Id: <1161446321.5230.69.camel@lappy> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: "Chen, Kenneth W" Cc: 'Hugh Dickins' , 'Andrew Morton' , linux-mm@kvack.org, arjan List-ID: On Thu, 2006-10-19 at 12:12 -0700, Chen, Kenneth W wrote: > Imprecise RSS accounting is an irritating ill effect with pt sharing. > After consulted with several VM experts, I have tried various methods to > solve that problem: (1) iterate through all mm_structs that share the PT > and increment count; (2) keep RSS count in page table structure and then > sum them up at reporting time. None of the above methods yield any > satisfactory implementation. > > Since process RSS accounting is pure information only, I propose we don't > count them at all for hugetlb page. rlimit has such field, though there is > absolutely no enforcement on limiting that resource. One other method is > to account all RSS at hugetlb mmap time regardless they are faulted or not. > I opt for the simplicity of no accounting at all. I do feel I must object to this. Especially with hugetlb getting real accessible with libhugetlbfs etc., I suspect administrators will shortly be confused where all their memory went. Also, like stated earlier, I don't like breaking RSS accounting now, and when we do have thought up a valid meaning for the field, again. You state correctly that RLIMIT_RSS is currently not enforced, but its an active area int that we do want to enforce it in the near future. I do grant its a very hard problem, comming up with a valid/meaningfull/workable definition of RSS, but I dislike this opt out of just not counting it at all - and thereby making the effort of enforcing RSS harder. Just my 0.02 eurocent ;-) -- 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